Internet DRAFT - draft-strassner-supa-generic-policy-info-model
draft-strassner-supa-generic-policy-info-model
Network Working Group J. Strassner
Internet Draft Huawei Technologies
Intended status: Standard Track J. Halpern
Expires: September 25, 2016 Ericsson
J. Coleman
Cisco Systems
March 21, 2016
Generic Policy Information Model for
Simplified Use of Policy Abstractions (SUPA)
draft-strassner-supa-generic-policy-info-model-05
Abstract
This document defines an information model for representing
policies using a common extensible framework that is independent
of language, protocol, repository. It is also independent of the
level of abstraction of the content and meaning of a policy.
Status of this Memo
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This Internet-Draft will expire on August 17, 2016.
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Table of Contents
1. Overview ....................................................... 9
1.1. Introduction .............................................. 9
1.2. Changes Since Version -03 ................................ 11
2. Conventions Used in This Document ............................. 11
3. Terminology ................................................... 12
3.1. Acronyms .................................................. 12
3.2. Definitions ............................................... 12
3.2.1. Core Terminology ..................................... 12
3.2.1.1. Information Model .............................. 12
3.2.1.2. Data Model ..................................... 13
3.2.1.3. Abstract Class ................................. 13
3.2.1.4. Concrete Class ................................. 13
3.2.1.5. Container ...................................... 13
3.2.1.6. PolicyContainer ................................ 13
3.2.2. Policy Terminology ................................... 14
3.2.2.1. SUPAPolicyObject ............................... 14
3.2.2.2. SUPAPolicy ..................................... 14
3.2.2.3. SUPAPolicyClause ............................... 14
3.2.2.4. SUPAECAPolicyRule .............................. 14
3.2.2.5. SUPAMetadata ................................... 15
3.2.2.6. SUPAPolicyTarget ............................... 15
3.2.2.7. SUPAPolicySource ............................... 15
3.2.3. Modeling Terminology ................................. 16
3.2.3.1. Inheritance .................................... 16
3.2.3.2. Relationship ................................... 16
3.2.3.3. Association .................................... 16
3.2.3.4. Aggregation .................................... 16
3.2.3.5. Composition .................................... 17
3.2.3.6. Association Class .............................. 17
3.2.3.7. Multiplicity ................................... 17
3.2.3.8. Navigability ................................... 17
3.3. Symbology ................................................ 18
3.3.1. Inheritance ......................................... 18
3.3.2. Association ......................................... 18
3.3.3. Aggregation ......................................... 19
3.3.4. Composition ......................................... 19
3.3.5. Association Class ................................... 19
3.3.6. Abstract vs. Concrete Classes ....................... 20
4. Policy Abstraction Architecture ............................... 21
4.1. Motivation ............................................... 22
4.2. SUPA Approach ............................................ 23
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4.3. SUPA Generic Policy Information Model Overview............ 23
4.3.1. SUPAPolicyObject .................................... 25
4.3.2. SUPAPolicyStructure ................................. 26
4.3.3. SUPAPolicyComponentStructure ........................ 26
4.3.4. SUPAPolicyClause .................................... 27
4.3.5. SUPAPolicyComponentDecorator ........................ 27
4.3.6. SUPAPolicyTarget .................................... 28
4.3.7. SUPAPolicySource .................................... 28
4.4. The Design of the GPIM ................................... 28
4.4.1. Structure of Policies ............................... 29
4.4.2. Representing an ECA Policy Rule ..................... 30
4.4.3. Creating SUPA Policy Clauses ........................ 33
4.4.4. Creating SUPAPolicyClauses .......................... 36
4.4.5. SUPAPolicySources ................................... 37
4.4.6. SUPAPolicyTargets ................................... 39
4.4.7. SUPAPolicyMetadata .................................. 39
4.4.7.1. Motivation ..................................... 39
4.4.7.2. Design Approach ................................ 40
4.4.7.2.1. Policies and Actors ....................... 42
4.4.7.2.2. Deployment vs. Execution of Policies ...... 43
4.4.7.2.3. Using SUPAMetadata for Policy Deployment
and Execution ............................. 43
4.4.7.3. Structure of SUPAPolicyMetadata ................ 44
4.5. Advanced Features ........................................ 47
4.5.1. Policy Grouping ..................................... 47
4.5.2. Policy Rule Nesting ................................. 47
5. GPIM Model ..................................................... 48
5.1. Overview .................................................. 48
5.2. The Abstract Class "SUPAPolicyObject" ..................... 49
5.2.1. SUPAPolicyObject Attributes .......................... 50
5.2.1.1. Object Identifiers ............................. 50
5.2.1.2. The Attribute "supaPolObjIDContent" ............. 51
5.2.1.3. The Attribute "supaPolObjIDEncoding" ............ 51
5.2.1.4. The Attribute "supaPolicyDescription" ........... 51
5.2.1.5. The Attribute "supaPolicyName" .................. 51
5.2.2. SUPAPolicy Relationships ............................ 52
5.2.2.1. The Relationship "SUPAHasPolicyMetadata" ....... 52
5.2.2.2. The Association Class
"SUPAHasPolicyMetadataDetail" .................. 52
5.3. The Abstract Class "SUPAPolicyStructure" ................. 52
5.3.1. SUPAPolicyStructure Attributes ...................... 53
5.3.1.1. The Attribute "supaPolAdminStatus" ............. 53
5.3.1.2. The Attribute "supaPolContinuumLevel" .......... 53
5.3.1.3. The Attribute "supaPolDeployStatus" ............ 54
5.3.1.4. The Attribute "supaPolExecStatus" .............. 54
5.3.1.5. The Attribute "supaPolExecFailStrategy" ........ 54
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5.3.2. SUPAPolicyStructure Relationships ................... 55
5.3.2.1. The Aggregation "SUPAHasPolicySource" .......... 55
5.3.2.2. The Association Class
"SUPAHasPolicySourceDetail" .................... 55
5.3.2.2.1. The Attribute "supaPolSrcIsAuthenticated" . 55
5.3.2.2.2. The Attribute "supaPolSrcIsTrusted" ....... 56
5.3.2.3. The Aggregation "SUPAHasPolicyTarget" .......... 56
5.3.2.4. The Association Class
"SUPAHasPolicyTargetDetail" ................... 56
5.3.2.4.1. The Attribute "supaPolTgtIsAuthenticated" . 56
5.3.2.4.2. The Attribute "supaPolTgtIsEnabled" ....... 56
5.3.2.5. The Association "SUPAHasPolExecFailTakeAction" . 57
5.3.2.6. The Association Class
"SUPAHasPolExecFailTakeActionDetail" ........... 57
5.3.2.6.1. The Attribute
"supaPolExecFailTakeActionEncoding" ....... 57
5.3.2.6.2. The Attribute
"supaPolExecFailTakeActionName[1..n]" ..... 58
5.3.2.7. The Aggregation "SUPAHasPolicyClause" .......... 58
5.3.2.8. The Association Class
"SUPAHasPolicyClauseDetail" .................... 58
5.4. The Abstract Class "SUPAPolicyComponentStructure" ........ 59
5.4.1. SUPAPolicyComponentStructure Attributes ............. 59
5.4.2. SUPAPolicyComponentStructure Relationships .......... 59
5.5. The Abstract Class "SUPAPolicyClause" .................... 59
5.5.1. SUPAPolicyClause Attributes ......................... 60
5.5.1.1. The Attribute "supaPolClauseExecStatus" ........ 60
5.5.2. SUPAPolicyClause Relationships ...................... 61
5.6. The Concrete Class "SUPAEncodedClause" ................... 61
5.6.1. SUPAEncodedClause Attributes ........................ 61
5.6.1.1. The Attribute "supaEncodedClauseContent" ....... 61
5.6.1.2. The Attribute "supaEncodedClauseEncoding" ...... 61
5.6.1.3. The Attribute "supaEncodedClauseResponse" ...... 62
5.6.2. SUPAEncodedClause Relationships ..................... 62
5.7. The Abstract Class "SUPAPolicyComponentDecorator" ........ 62
5.7.1. The Decorator Pattern ............................... 63
5.7.2. SUPAPolicyComponentDecorator Attributes ............. 64
5.7.2.1. The Attribute "supaPolCompConstraintEncoding" .. 64
5.7.2.2. The Attribute "supaAPolCompConstraint[0..n]" ... 64
5.7.3. SUPAPolicyComponentDecorator Relationships .......... 65
5.7.3.1. The Aggregation
"SUPAHasDecoratedPolicyComponent" .............. 65
5.7.3.2. The Association Class
"SUPAHasDecoratedPolicyComponentDetail" ........ 65
5.7.3.2.1. The Attribute
"supaDecoratedConstraintEncoding" ......... 65
5.7.3.2.2. The Attribute
"supaDecoratedConstraint[0..n]" ........... 66
5.7.4. Illustration of Constraints in the Decorator Pattern 66
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5.8. The Abstract Class "SUPAPolicyTerm" ...................... 67
5.8.1. SUPAPolicyTerm Attributes ........................... 68
5.8.1.1. The Attribute "supaPolTermIsNegated" ........... 68
5.8.2. SUPAPolicyTerm Relationships ........................ 68
5.9. The Concrete Class "SUPAPolicyVariable" .................. 68
5.9.1. Problems with the RFC3460 Version of PolicyVariable . 69
5.9.2. SUPAPolicyVariable Attributes ....................... 69
5.9.2.1. The Attribute "supaPolVarName" ................. 69
5.9.3. SUPAPolicyVariable Relationships .................... 69
5.10. The Concrete Class "SUPAPolicyOperator" ................. 69
5.10.1. Problems with the RFC3460 Version .................. 70
5.10.2. SUPAPolicyOperator Attributes ...................... 70
5.10.2.1. The Attribute "supaPolOpType" ................. 70
5.10.3. SUPAPolicyOperator Relationships ................... 70
5.11. The Concrete Class "SUPAPolicyValue" .................... 71
5.11.1. Problems with the RFC3460 Version of PolicyValue ... 71
5.11.2. SUPAPolicyValue Attributes ......................... 71
5.11.2.1. The Attribute "supaPolValContent[0..n]" ....... 71
5.11.2.2. The Attribute "supaPolValEncoding" ............ 72
5.11.3. SUPAPolicyValue Relationships ...................... 72
5.12. The Concrete Class "SUPAGenericDecoratedComponent" ...... 72
5.12.1. SUPAGenericDecoratedComponent Attributes ........... 73
5.12.1.1. The Attribute
"supaVendorDecoratedCompContent[0..n]" ......... 73
5.12.1.2. The Attribute "supaVendorDecoratedCompEncoding" 73
5.12.2. SUPAGenericDecoratedComponent Relationships ........ 73
5.13. The Concrete Class "SUPAPolicyCollection" ............... 74
5.13.1. Motivation ......................................... 74
5.13.2. Solution ........................................... 74
5.13.3. SUPAPolicyCollection Attributes .................... 75
5.13.3.1. The Attribute "supaPolCollectionContent[0..n]" 75
5.13.3.2. The Attribute "supaPolCollectionEncoding" ..... 75
5.13.3.3. The Attribute "supaPolCollectionFunction" ..... 75
5.13.3.4. The Attribute "supaPolCollectionIsOrdered" .... 75
5.13.3.5. The Attribute "supaPolCollectionType" ......... 76
5.13.4. SUPAPolicyCollection Relationships ................. 77
5.14. The Concrete Class "SUPAPolicySource" ..................... 77
5.14.1. SUPAPolicySource Attributes ........................ 77
5.14.2. SUPAPolicySource Relationships ..................... 77
5.15. The Concrete Class "SUPAPolicyTarget" ................... 77
5.15.1. SUPAPolicyTarget Attributes ........................ 78
5.15.2. SUPAPolicyTarget Relationships ..................... 78
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5.16. The Abstract Class "SUPAPolicyMetadata" ................. 78
5.16.1. SUPAPolicyMetadata Attributes ...................... 79
5.16.1.1. The Attribute "supaPolMetadataDescription" .... 79
5.16.1.2. The Attribute "supaPolMetadataIDContent" ...... 79
5.16.1.3. The Attribute "supaPolMetadataIDEncoding" ..... 79
5.16.1.4. The Attribute "supaPolMetadataName" ........... 80
5.16.2. SUPAPolicyMetadata Relationships ................... 80
5.16.2.1. The Aggregation "SUPAHasPolicyMetadata" ....... 80
5.16.2.2. The Abstract Class
"SUPAHasPolicyMetadataDetail" ................. 80
5.16.2.2.1. The Attribute
"supaPolMetadataIsApplicable" ............ 80
5.16.2.2.2. The Attribute
"supaPolMetadataConstraintEncoding" ...... 81
5.16.2.2.3. The Attribute
"supaPolMetadataConstraint[0..n]" ........ 81
5.17. The Concrete Class "SUPAPolicyConcreteMetadata" ......... 81
5.17.1. SUPAPolicyConcreteMetadata Attributes .............. 82
5.17.2. SUPAPolicyConcreteMetadata Relationships ........... 82
5.18. The Abstract Class "SUPAPolicyMetadataDecorator" ........ 82
5.18.1. SUPAPolicyMetadataDecorator Attributes ............. 82
5.18.1.1. The Attribute "supaPolMDValidPeriodEnd" ....... 82
5.18.1.2. The Attribute "supaPolMDValidPeriodStart" ..... 82
5.18.2. SUPAPolicyMetadataDecorator Relationships .......... 82
5.18.2.1. The Aggregation "HasSUPAMetadataDecorator" .... 83
5.18.2.2. The Association Class
"HasSUPAMetadataDecoratorDetail" .............. 83
5.19. The Concrete Class "SUPAPolicyAccessMetadataDef" ........ 83
5.19.1. SUPAPolicyAccessMetadataDef Attributes ............. 84
5.19.1.1. The Attribute "supaAccessPrivilegeDef" ........ 84
5.19.1.2. The Attribute "supaAccessPrivilegeModelName" .. 84
5.19.1.3. The Attribute "supaAccessPrivilegeModelRef" ... 85
5.20. The Concrete Class "SUPAPolicyVersionMetadataDef" ....... 85
5.20.1. SUPAPolicyVersionMetadataDef Attributes ............ 85
5.20.1.1. The Attribute "supaVersionMajor" .............. 85
5.20.1.2. The Attribute "supaVersionMinor" .............. 86
5.20.1.3. The Attribute "supaVersionRelType" ............ 86
5.20.1.4. The Attribute "supaVersionTypeNum" ............ 86
6. SUPA ECAPolicyRule Information Model .......................... 87
6.1. Overview ................................................. 87
6.2. Constructing a SUPAECAPolicyRule ......................... 88
6.3. Working With SUPAECAPolicyRules .......................... 89
6.4. The Abstract Class "SUPAECAPolicyRule" ................... 91
6.4.1. SUPAECAPolicyRule Attributes ........................ 92
6.4.1.1. The Attribute "supaECAPolicyRulePriority" ...... 93
6.4.1.2. The Attribute "supaECAPolicyRuleStatus" ........ 93
6.4.2. SUPAECAPolicyRule Relationships ..................... 93
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6.5. The Concrete Class "SUPAECAPolicyRuleAtomic" ............. 93
6.5.1. SUPAECAPolicyRuleAtomic Attributes .................. 93
6.5.2. SUPAECAPolicyRuleAtomic Relationships ............... 93
6.6. The Concrete Class "SUPAECAPolicyRuleComposite" .......... 94
6.6.1. SUPAECAPolicyRuleComposite Attributes ............... 94
6.6.1.1. The Attribute "supaECAEvalStrategy" ............ 94
6.6.2. SUPAECAPolicyRuleComposite Relationships ............ 95
6.6.2.1. The Aggregation "SUPAHasECAPolicyRule" ......... 95
6.6.3. The Association Class "SUPAHasECAPolicyRuleDetail" .. 95
6.6.3.1. The Attribute "supaECAPolicyIsDefault" ......... 95
6.7. The Abstract Class "SUPABooleanClause" ................... 96
6.7.1. SUPABooleanClause Attributes ........................ 96
6.7.1.1. The Attribute "supaBoolClauseIsNegated" ........ 97
6.7.2. SUPABooleanClause Relationships ..................... 97
6.8. The Concrete Class "SUPABooleanClauseAtomic" ............. 97
6.8.1. SUPABooleanClauseAtomic Attributes .................. 97
6.8.2. SUPABooleanClauseAtomic Relationships ............... 97
6.9. The Concrete Class "SUPABooleanClauseComposite" .......... 97
6.9.1. SUPABooleanClauseComposite Attributes ................ 98
6.9.1.1. The Attribute "supaBoolClauseBindValue" ........ 98
6.9.1.2. The Attribute "supaBoolClauseIsCNF" ............ 98
6.9.2. SUPABooleanClauseComposite Relationships ............ 98
6.9.2.1. The Aggregation "SUPAHasBooleanClause" ......... 98
6.9.3. The Concrete Class "SUPAHasBooleanClauseDetail" ..... 99
6.9.3.1. SUPAHasBooleanClauseDetail Attributes .......... 99
6.10. The Abstract Class "SUPAECAComponent" ................... 99
6.10.1. SUPAECAComponent Attributes ........................ 99
6.10.1.1. The Attribute supaECACompIsTerm .............. 100
6.10.2. SUPAECAComponent Relationships .................... 100
6.11. The Concrete Class "SUPAPolicyEvent" ................... 100
6.11.1. SUPAPolicyEvent Attributes ........................ 100
6.11.1.1. The Attribute "supaPolicyEventIsPreProcessed" 100
6.11.1.2. The Attribute "supaPolicyEventIsSynthetic" ... 100
6.11.1.3. The Attribute "supaPolicyEventTopic[0..n]" ... 101
6.11.1.4. The Attribute "supaPolicyEventEncoding[1..n]" 101
6.11.1.5. The Attribute "supaPolicyEventData[1..n]" .... 101
6.11.2. SUPAPolicyEvent Relationships ..................... 101
6.12. The Concrete Class "SUPAPolicyCondition" ............... 102
6.12.1. SUPAPolicyCondition Attributes .................... 102
6.12.1.1. The Attribute "supaPolicyConditionData[1..n]" 102
6.12.1.2. The Attribute "supaPolicyConditionEncoding" .. 102
6.12.2. SUPAPolicyEvent Relationships ..................... 102
6.13. The Concrete Class "SUPAPolicyAction" .................. 103
6.13.1. SUPAPolicyAction Attributes ....................... 103
6.13.1.1. The Attribute "supaPolicyActionData[1..n]" ... 103
6.13.1.2. The Attribute "supaPolicyActionEncoding" ..... 104
6.13.2. SUPAPolicyAction Relationships .................... 104
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7. Examples ...................................................... 104
8. Security Considerations ...................................... 104
9. IANA Considerations ........................................... 105
10. Acknowledgments .............................................. 105
11. References ................................................... 105
11.1. Normative References .................................... 105
11.2. Informative References ................................. 105
Authors' Addresses ............................................... 107
Appendix A. Brief Analyses of Previous Policy Work .............. 107
Appendix B. Mathematical Logic Terminology and Symbology ........ 114
Appendix C. SUPA Logic Statement Information Model .............. 114
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1. Overview
This document defines an information model for representing
policies using a common extensible framework that is independent
of language, protocol, repository, and the level of abstraction of
the content and meaning of a policy. This enables a common set of
concepts defined in this information model to be mapped into
different representations of policy (e.g., procedural, imperative,
and declarative). It also enables different data models that use
different languages, protocols, and repositories to optimize
their usage. The definition of common policy concepts also
provides better interoperability by ensuring that each data
model can share a set of common concepts, independent of its
level of detail or the language, protocol, and/or repository
that it is using. It is also independent of the target data
model that will be generated.
This version of the information model focuses on defining one
type of policy rule: the event-condition-action (ECA) policy rule.
Accordingly, this document defines two sets of model elements:
1. A framework for defining the concept of policy,
independent of how policy is represented or used; this is
called the SUPA Generic Policy Information Model (GPIM)
2. A framework for defining a policy model that uses the
event-condition-action paradigm; this is called the SUPA
Eca Policy Rule Information Model (EPRIM), and extends
concepts from the GPIM.
The combination of the GPIM and the EPRIM provides an extensible
framework for defining policy that uses an event-condition-action
representation that is independent of data repository, data
definition language, query language, implementation language, and
protocol.
The Appendices describe how the structure of the GPIM defines a
set of generic concepts that enables other types of policies, such
as declarative (or "intent-based") policies, to be added later.
1.1. Introduction
Simplified Use of Policy Abstractions (SUPA) defines an interface
to a network management function that takes high-level, possibly
network-wide policies as input and creates element configuration
snippets as output. SUPA addresses the needs of operators and
application developers to represent multiple types of policy
rules, which vary in the level of abstraction, to suit the needs
of different actors [1], [10].
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Different constituencies of users would like to use languages that
use terminology and concepts that are familiar to each constituency.
Rather than require multiple software systems to be used for each
language, a common information model enables these different
languages to be mapped to terms in the information model. This
facilitiates the use of a single software system to generate data
models for each language. In the example shown in Figure 1 (which
is a simplified policy continuum [10]), each constituency needs
different grammars using different concepts and terminologies to
match their skill set. This is shown in Figure 1. A unified
information model is one way to build a consensual lexicon that
enables terms from one language to be mapped to terms of another
language.
+---------------------+
+---------------+ \| High-level Policies | \+-------------+
| Business User |----| Without Technical |----| Language #1 |
+---------------+ /| Terminology | /+-------------+
+---------------------+
+---------------------+
+---------------+ \| Policies That Use | \+-------------+
| Developer |----| Classes, Attributes,|----| Language #2 |
+---------------+ /| Relationships, ... | /+-------------+
+---------------------+
... ... ...
+---------------------+
+---------------+ \| Low-level Policies | \+-------------+
| Admin |----| with Technology- |----| Language #n |
+---------------+ /| Specific Terms in a | /+-------------+
| Specific Language |
+---------------------+
Figure 1. Different Constituencies Need Different Policies
More importantly, an information model defines concepts in a
uniform way, enabling formal mapping processes to be developed to
translate the information model to a set of data models. This
simplifies the process of constructing software to automate the
policy management process. It also simplifies the language
generation process, though that is beyond the scope of this
document.
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This common framework takes the form of an information model that
is divided into one high-level module and any number of lower-
level modules, where each lower-level module extends the concepts
of the single high-level module. Conceptually, a set of model
elements (e.g., classes, attributes, and relationships) are used
to define the Generic Policy Information Model (GPIM); this module
defines a common set of policy management concepts that are
independent of the type of policy (e.g., imperative, procedural,
declarative, or otherwise). Then, any number of additional modules
are derived from the GPIM; each additional module MUST extend the
GPIM to define a new type of policy rule by adding to the GPIM.
(Note: using extensions preserves the core interoperability, as
compared with modification of the base GPIM, which would adversely
compromise interoperability.
The SUPA Eca Policy Rule Information Model (EPRIM) extends the
GPIM to represent policy rules that use the Event-Condition-Action
(ECA) paradigm. (The Appendices describe the SUPA Logic Statement
Information Model (LSIM), which shows how to extend the GPIM to
represent a collection of statements that are either Propositional
Logic (PL) or First-Order Logic (FOL), respectively. Both of these
logics are types of declarative logic. Note that the LSIM is
currently out of scope. However, it is outlined as a set of
Appendices in this document to get feedback on its utility.
1.2. Changes Since Version -04
There are several changes in this version of this document
compared to the previous versions of this document. They are:
1) The SUPAVendorDecoratedComponent class has been renamed to
SUPAGenericDecoratedComponent, and its function has been
made more generic.
2) A number of clarifications have been made in response to
questions from the SUPA mailing list.
3) The multiplicity of all relationships have been fine-tuned
4) A **preliminary** YANG model [RFC6020] [RFC6991] has been
built from the GPIM; see [15].
5) Various additional typos have been fixed.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in [RFC2119]. In
this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to
be interpreted as carrying [RFC2119] significance.
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3. Terminology
This section defines acronyms, terms, and symbology used in the
rest of this document.
3.1. Acronyms
CLI Command Line Interface
CRUD Create, Read, Update, Delete
CNF Conjunctive Normal Form
DNF Disjunctive Normal Form
ECA Event-Condition-Action
EPRIM (SUPA) ECA Policy Rule Information Model
GPIM (SUPA) Generic Policy Information Model
OAM&P Operations, Administration, Management, and Provisioning
OID Object IDentifier
SUPA Simplified Use of Policy Abstractions
TMF TeleManagent Forum (TM Forum)
UML Unified Modeling Language
URI Uniform Resource Identifier
YANG A data definition language for use with NETCONF
ZOOM Zero-touch Orchestration, Operations, and Management
(a TMF project that also works on information models)
3.2. Definitions
This section defines the terminology that is used in this document.
3.2.1. Core Terminology
The following subsections define the terms "information model" and
"data model", as well as "container" and "policy container".
3.2.1.1. Information Model
An information model is a representation of concepts of interest
to an environment in a form that is independent of data repository,
data definition language, query language, implementation language,
and protocol.
Note: this definition is more specific than that of [RFC3198], so
as to focus on the properties of information models. That definition
was: "An abstraction and representation of the entities in a managed
environmentl, their properties, attributes and operations, and the
way that they relate to each other. It is independent of any
specific repository, software usage, protocol, or platform."
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3.2.1.2. Data Model
A data model is a representation of concepts of interest to an
environment in a form that is dependent on data repository, data
definition language, query language, implementation language, and
protocol (typically, but not necessarily, all three).
Note: this definition is more specific than that of [RFC3198], so
as to focus on the properties of data models that are generated
from information models. That definition was: "A mapping of the
contents of an information model into a form that is specific to a
particular type of data store or repository."
3.2.1.3. Abstract Class
An abstract class is a class that cannot be directly instantiated.
It MAY have abstract or concrete subclasses. It is denoted with a
capital A near the top-left side of the class.
3.2.1.4. Concrete Class
A concrete class is a class that can be directly instantiated. Note
that classes are either abstract or concrete. In addition, once a
class has been defined as concrete in the hierarchy, all of its
subclasses MUST also be concrete. It is denoted with a capital C
near the top-left side of the class.
3.2.1.5. Container
A container is an object whose instances may contain zero or more
additional objects, including container objects. A container
provides storage, query, and retrieval of its contained objects
in a well-known, organized way.
3.2.1.6. PolicyContainer
In this document, a PolicyContainer is a special type of container
that provides at least the following three functions:
1. It uses metadata to define how its content is interpreted
2. It separates the content of the policy from the
representation of the policy
3. It provides a convenient control point for OAMP operations
The combination of these three functions enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
This document does NOT define a specific data type to implementation
a PolicyContainer, as many different types of data types can be
used. However, the data type chosen SHOULD NOT allow duplicate
members in the PolicyContainer. In addition, order is irrelevant,
since priority will override any initial order of the members of
this PolicyContainer.
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3.2.2. Policy Terminology
The following terms define different policy concepts used in the
SUPA Generic Policy Information Model (GPIM). Note that the
prefix "SUPA" is used for all classes and relationships defined
in this model to ensure name uniqueness. Similarly, the prefix
"supa" is defined for all SUPA class attributes.
3.2.2.1. SUPAPolicyObject
A SUPAPolicyObject is the root of the GPIM class hierarchy. It is
an abstract class that all classes inherit from, except the
SUPAPolicyMetadata class.
3.2.2.2. SUPAPolicy
A SUPAPolicy is, in this version of this document, an ECA policy
rule that is a type of PolicyContainer. The PolicyContainer MUST
contain an ECA policy rule, SHOULD contain one or more
SUPAPolicyMetadata objects, and MAY contain other elements that
define the semantics of the policy rule. Policies are generically
defined as a means to monitor and control the changing and/or
maintaining of the state of one or more managed objects [1]. In
this context, "manage" means that at least create, read, query (a
more complex operation than read that may involve pre- and/or post-
processing of the results of the operation), update, and delete
functions are supported.
3.2.2.3. SUPAPolicyClause
A SUPAPolicyClause is an abstract class. Its subclasses define
different types of clauses that are used to create the content
for different types of SUPAPolicies.
For example, the SUPABooleanClause subclass models the content
of a SUPAPolicy as a Boolean clause, where each Boolean clause
is made up of a set of reusable objects. In contrast, a
SUPAEncodedClause encodes the entire clause as a set of
attributes. All types of SUPAPolicies MUST use one or more
SUPAPolicyClauses to construct a SUPAPolicy.
3.2.2.4. SUPAECAPolicyRule
An Event-Condition-Action (ECA) Policy (SUPAECAPolicyRule) is an
abstract class that is a type of PolicyContainer. It represents
a policy rule as a three-tuple, consisting of an event, a
condition, and an action clause. In an information model, this
takes the form of three different aggregations, one for each
clause. Each clause MUST be represented by at least one
SUPAPolicyClause. Optionally, the SUPAECAPolicyRule MAY contain
zero or more SUPAPolicySources, zero or more SUPAPolicyTargets,
and zero or more SUPAPolicyMetadata objects.
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3.2.2.5. SUPAMetadata
Metadata is, literally, data about data. SUPAMetadata is an
abstract class that contains prescriptive and/or descriptive
information about the object(s) to which it is attached. While
metadata can be attached to any information model element, this
document only considers metadata attached to classes and
relationships.
When defined in an information model, each instance of the
SUPAMetadata class MUST have its own aggregation relationship
with the set of objects that it applies to. However, a data model
MAY map these definitions to a more efficient form (e.g.,
flattening the object instances into a single object instance).
3.2.2.6. SUPAPolicyTarget
SUPAPolicyTarget is an abstract class that defines a set of
managed objects that may be affected by the actions of a
SUPAPolicyClause. A SUPAPolicyTarget may use one or more
mechanisms to identify the set of managed objects that it
affects; examples include OIDs and URIs.
When defined in an information model, each instance of the
SUPAPolicyTarget class MUST have its own aggregation
relationship with each SUPAPolicy that uses it. However, a
data model MAY map these definitions to a more efficient form
(e.g., flattening the SUPAPolicyTarget, SUPAMetadata, and
SUPAPolicy object instances into a single object instance).
3.2.2.7. SUPAPolicySource
SUPAPolicySource is an abstract class that defines a set of
managed objects that authored this SUPAPolicyClause. This is
required for auditability. A SUPAPolicySource may use one or more
mechanisms to identify the set of managed objects that authored it;
examples include OIDs and URIs. Specifically, policy CRUD MUST be
subject to authentication and authorization, and MUST be auditable.
Note that the mechanisms for doing these three operations are
currently not included, and are for further discussion.
When defined in an information model, each instance of the
SUPAPolicySource class MUST have its own aggregation relationship
with each SUPAPolicy that uses it. However, a data model MAY map
these definitions to a more efficient form (e.g., flattening the
SUPAPolicySource, SUPAMetadata, and SUPAPolicy object instances
into a single object instance).
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3.2.3. Modeling Terminology
The following terms define different types of relationships used
in the information models of the SUPA Generic Policy Information
Model (GPIM).
3.2.3.1. Inheritance
Inheritance makes an entity at a lower level of abstraction (e.g.,
the subclass) a type of an entity at a higher level of abstraction
(e.g., the superclass). Any attributes and relationships that are
defined for the superclass are also defined for the subclass.
However, a subclass does NOT change the characteristics or behavior
of the attributes or relationships of the superclass that it
inherits from. Formally, this is called the Liskov Substitution
Principle [7]. This principle is one of the key characteristics
that is NOT followed in [4], [6], [RFC3060], and [RFC3460].
A subclass MAY add new attributes and relationships that refine
the characteristics and/or behavior of it compared to its
superclass. A subclass MUST NOT change inherited attributes or
relationships.
3.2.3.2. Relationship
A relationship is a generic term that represents how a first set
of entities interact with a second set of entities. A recursive
relationship sets the first and second entity to the same entity.
There are three basic types of relationships, as defined in the
subsections below: associations, aggregations, and compositions.
A subclass MUST NOT change the multiplicity (see section 3.2.3.7)
of a relationship that it inherits. A subclass MUST NOT change any
attributes of a relation that it inherits that is realized using
an association class (see section 3.2.3.6).
3.2.3.3. Association
An association represents a generic dependency between a first
and a second set of entities. In an information model, an
association MAY be represented as a class.
3.2.3.4. Aggregation
An aggregation is a stronger type (i.e., more restricted
semantically) of association, and represents a whole-part
dependency between a first and a second set of entities. Three
objects are defined by an aggregation: the first entity, the
second entity, and a new third entity that represents the
combination of the first and second entities.
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The entity owning the aggregation is referred to as the
"aggregate", and the entity that is aggregated is referred to as
the "part". In an information model, an aggregation MAY be
represented as a class.
3.2.3.5. Composition
A composition is a stronger type (i.e., more restricted
semantically) of aggregation, and represents a whole-part
dependency with two important behaviors. First, an instance of the
part is included in at most one instance of the aggregate at a
time. Second, any action performed on the composite entity (i.e.,
the aggregate) is propagated to its constituent part objects.
For example, if the composite entity is deleted, then all of its
constituent part entities are also deleted. This is not true of
aggregations or associations - in both, only the entity being
deleted is actually removed, and the other entities are unaffected.
In an information model, a composition MAY be represented as
a class.
3.2.3.6. Association Class
A relationship may be implemented as an association class. This is
used to define the relationship as having its own set of features.
More specifically, if the relationship is implemented as an
association class, then the attributes of the association class, as
well as other relationships that the association class participates
in, may be used to define the semantics of the relationship. If the
relationship is not implemented as an association class, then no
additional semantics (beyond those defined by the type of the
relationship) are expressed by the relationship.
3.2.3.7. Multiplicity
A specification of the range of allowable cardinalities that a set
of entities may assume. This is always a pair of ranges, such as
1 - 1 or 0..n - 2..5.
3.2.3.8. Navigability
A relationship may have a restriction on the ability of an object
at one end of the relationship to access the object at the other
end of the relationship. This document defines two choices:
1. Each object is navigable by the other, which is indicated
by NOT providing any additional symbology, or
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2. An object A can navigate to object B, but object B cannot
navigate to object A. This is indicated by an open-headed
arrow pointing to the object that cannot navigate to the
other object. In this example, the arrow would be pointing
at object B.
Examples of navigability are:
+---------+ 3..4 +---------+
| | 1..2 \| |
| Class A |--------------| Class B |
| | /| |
+---------+ +---------+
This is an association. Class A can navigate to Class B, but Class
B cannot navigate to Class A. This is a mandatory association,
since none of the multiplicities contain a '0'. This association
reads as follows:
Class A depends on 3 to 4 instances of Class B, and
Class B depends on 1 to 2 instances of Class A.
3.3. Symbology
The following symbology is used in this document:
3.3.1. Inheritance
Inheritance: a subclass inherits the attributes and relationships
of its superclass, as shown below:
+------------+
| Superclass |
+------+-----+
/ \
I
I
I
+------+-----+
| Subclass |
+------------+
3.3.2. Association
Association: Class B depends on Class A, as shown below:
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+---------+ +---------+
+---------+ +---------+ | | \| |
| Class A |------| Class B | | Class A |------| Class B |
+---------+ +---------+ | | /| |
+---------+ +---------+
association with no association with
navigability restrictions navigability restrictions
3.3.3. Aggregation
Aggregation: Class B is the part, Class A is the aggregate,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | A ---| Class B | | Class A | A ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
aggregation with no aggregation with
navigability restrictions navigability restrictions
3.3.4. Composition
Composition: Class B is the part, Class A is the composite,
as shown below:
+---------+ +---------+ +---------+
| |/ \ +---------+ | |/ \ \| |
| Class A | C ---| Class B | | Class A | C ------| Class B |
| |\ / +---------+ | |\ / /| |
+---------+ +---------+ +---------+
composition with no composition with
navigability restrictions navigability restrictions
3.3.5. Association Class
Association Class: Class C is the association class implementing
the relationship D between classes A and B
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+---------+ +---------+
| Class A |----+-----| Class B |
+---------+ ^ +---------+
|
|
+----------+----------+
| Association Class C |
+---------------------+
3.3.6. Abstract vs. Concrete Classes
In UML, abstract classes are denoted with their name in italics.
For this draft, a capital 'A' will be placed at either the top
left or right corner of the class to signify that the class is
abstract. Similarly, a captial 'C' will be placed in the same
location to represent a concrete class. This is shown below.
A C
+---------+ +---------+
| Class A | | Class B |
+---------+ +---------+
An Abstract Class A Concrete Class
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4. Policy Abstraction Architecture
This section describes the motivation for the policy abstractions
that are used in SUPA. The following abstractions are provided:
o The GPIM defines a technology-neutral information model that
can express the concept of Policy.
o All classes, except for SUPAPolicyMetadata, inherit from
SUPAPolicyObject, or one of its subclasses
o SUPAPolicyObject and SUPAPolicyMetadata are designed to
inherit from classes in another model; the GPIM does not
define an "all-encompassing" model.
o This version of this document restricts the expression of
Policy to a set of event-condition-action clauses.
o Each clause is defined as a Boolean expression, and is a
reusable object
o Clauses may be combined to form more complex Boolean
expressions
o The purpose of the GPIM is to enable different policies that
have fundamentally different representations to share common
model elements. Policy statmeents, which are implemented as
instances of the SUPAPolicyClause class, separates the content
of a Policy from its representation. This is supported by:
o All policy rules (of which SUPAECAPolicyRule is the
first example of a concrete class) are derived from
the SUPAPolicyStructure class.
o All objects that are components of policy rules are
derived from the SUPAPolicyComponentStructure class.
o A SUPAPolicy MUST contain at least one SUPAPolicyClause.
o A SUPAPolicy MAY specify one or more SUPAPolicyTarget,
SUPAPolicySource, and SUPAPolicyMetadata objects to
augment the semantics of the SUPAPolicy
o A SUPAPolicyClause has two subclasses:
o A SUPABooleanClause, which is used to build
SUPAECAPolicyRules from reusable objects.
o A SUPAEncodedClause, which is used for using
attributes instead of objects to construct a
SUPAECAPolicyRule.
o A SUPAECAPolicyRule defines the set of events and conditions
that are responsible for executing its actions; it MUST have
at least one event clause, at least one condition clause, and
at least one action clause.
o The action(s) of a SUPAECAPolicyRule are ONLY executed
if both the event and condition clauses evaluate to TRUE
o A SUPAPolicyAction MAY invoke another SUPAECAPolicyRule
(see section 6.13).
o SUPAMetadata MAY be defined for any SUPAPolicyObject class.
o SUPAMetadata MAY be prescriptive and/or descriptive in nature.
Please see the Appendices for experimental definitions of
declarative policies. Note that they also are derived from the
GPIM, and extend (but do not change) the above abstractions.
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4.1. Motivation
The power of policy management is its applicability to many
different types of systems. There are many different actors that
can use a policy management system, including end-users, operators,
application developers, and administrators. Each of these
constituencies have different concepts and skills, and use
different terminology. For example, an operator may want to express
an operational rule that states that only Platinum and Gold users
can use streaming multimedia applications. As a second example, a
network administrator may want to define a more concrete policy
rule that looks at the number of dropped packets and, if that
number exceeds a programmable threshold, changes the queuing and
dropping algorithms used.
SUPA may be used to define other types of policies, such as for
systems and operations management; an example is: "All routers and
switches must have password login disabled". See section 3 of [8]
for additional declarative and ECA policy examples.
All of the above examples are commonly referred to as "policy
rules", but they take very different forms, since they are at very
different levels of abstraction and typically authored by
different actors. The first was very abstract, and did not contain
any technology-specific terms, while the second was more concrete,
and likely used technical terms of a general (e.g., IP address
range, port numbers) as well as a vendor-specific nature (e.g.,
specific queuing, dropping, and/or scheduling algorithms
implemented in a particular device). The third restricted the type
of login that was permissible for certain types of devices in the
environment.
Note that the first two policy rules could directly affect each
other. For example, Gold and Platinum users might need different
device configurations to give the proper QoS markings to their
streaming multimedia traffic. This is very difficult to do if a
common policy model does not exist, especially if the two policies
are authored by different actors that use different terminology
and have different skill sets. More importantly, the users of
these two policies likely have different job responsibilities.
They may have no idea of the concepts used in each policy. Yet,
their policies need to interact in order for the business to
provide the desired service. This again underscores the need for
a common policy framework.
Certain types of policy rules (e.g., ECA) may express actions, or
other types of operations, that contradict each other. SUPA
provides a rich object model that can be used to support language
definitions that can find and resolve such problems.
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4.2. SUPA Approach
The purpose of the SUPA Generic Policy Information Model (GPIM) is
to define a common framework for expressing policies at different
levels of abstraction. SUPA uses the GPIM as a common vocabulary
for representing policy concepts that are independent of language,
protocol, repository, and level of abstraction. This enables
different actors to author and use policies at different levels of
abstraction. This forms a policy continuum [1] [2], where more
abstract policies can be translated into more concrete policies,
and vice-versa.
Most systems define the notion of a policy as a single entity.
This assumes that all users of policy have the same terminology,
and use policy at the same level of abstraction. This is rarely,
if ever, true in modern systems. The policy continuum defines a
set of views (much like RM-ODP's viewpoints [9]) that are each
optimized for a user playing a specific role. SUPA defines the
GPIM as a standard vocabulary and set of concepts that enable
different actors to use different formulations of policy. This
corresponds to the different levels in the policy continuum, and
as such, can make use of previous experience in this area.
It may be necessary to translate a Policy from a general to a more
specific form (while keeping the abstraction level the same). For
example, the declarative policy "Every network attached to a VM
must be a private network owned by someone in the same group as
the owner of the VM" may be translated to more formal form (e.g.,
Datalog (as in OpenStack Congress). It may also be necessary to
translate a Policy to a different level of abstraction. For
example, the previous Policy may need to be translated to a form
that network devices can process directly. This requires a common
framework for expressing policies that is independent of the level
of abstraction that a Policy uses.
4.3. SUPA Generic Policy Information Model Overview
Figure 2 illustrates the approach for representing policy rules
in SUPA. The top two layers are defined in this document; the
bottom layer (Data Models) are defined in separate documents.
Conceptually, the GPIM defines a set of objects that define the
key elements of a Policy independent of how it is represented or
its content. As will be shown, there is a significant difference
between SUPAECAPolicyRules (see Section 6) and other types of
policies (see Section 7). In principle, other types of SUPAPolicies
could be defined, but the current charter is restricted to using
only event-condition-action SUPAPolicies as exemplars.
Note: the GPIM MAY be used without the EPRIM. However, in order to
use the EPRIM, the GPIM MUST also be used.
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+----------------------------------------------+
| SUPA Generic Policy Information Model (GPIM) |
+----------------------+-----------------------+
/ \
|
|
+-----------------+--------------+
| |
| |
+-----------+---------------+ +-------------+-------------+
| SUPAECAPolicyRule | | Other Policy Models that |
| Information Model (EPRIM) | | are Derived from the GPIM |
+-----------+---------------+ +-------------+-------------+
/ \ / \
| |
| |
+-----------+-----------+ +-----------+------------+
| ECAPolicyRule | | Other Types of |
| Data Model | | Data Models |
+-----------------------+ +------------------------+
Figure 2. Overview of SUPA Policy Rule Abstractions
This draft defines the GPIM and EPRIM. Note that there is only
ONE GPIM and ONE EPRIM. While both can be extended, it is
important to limit the number of information models to one, in
order to avoid defining conflicting concepts at this high a
level of abstraction. Similarly, if the GPIM and EPRIM are part
of another information model, then they should collectively
still define a single information model. The GPIM defines the
following concepts:
o A class defining the top of the GPIM class hierarchy, called
SUPAPolicyObject
o Four subclasses of SUPAPolicyObject, representing:
o the top of the PolicyRule hierarchy, called
SUPAPolicyStructure
o the top of the PolicyRule component hierarchy, called
SUPAPolicyComponentStructure
o PolicySource
o PolicyTarget
The SUPAPolicyStructure class is the superclass for all types of
Policies (e.g., imperative, declarative, and others). This
document is currently limited to imperative (e.g., ECA) policies.
However, care has been taken to ensure that the attributes and
relationships of the SUPAPolicyStructure class are extensible,
and can be used for more types of policies than just ECA policies.
This yields the following high-level structure:
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A
+------------------+
| SUPAPolicyObject |
+--------+---------+
/ \
I
I
+----------------+--------------------+
I I I
A I I A I
+--------+------------+ I +------------+-----------------+
| SUPAPolicyStructure | I | SUPAPolicyComponentStructure |
+----+----------------+ I +------------+-----------------+
/ \ I / \
I +--------+----+ I
I I I I
I C I I I
I +-------+----------+ I I
I | SUPAPolicySource | I I
I +------------------+ I I
I I I
I +-------------+ I
I I I
I C I +-----+-------+
I +-------+----------+ I I
I | SUPAPolicyTarget | A I I
I +------------------+ +--------+---------+ I
A I | SUPAPolicyClause | I
+-----+------------+ +------------------+ I
| SUPAECAPolicyRule| I
+------------------+ A I
+--------------------+---------+
| SUPAPolicyComponentDecorator |
+------------------------------+
Figure 3. Functional View of the Top-Level GPIM
Note that all classes except the SUPAPolicySource and the
SUPAPolicyTarget classes are defined as abstract. This provides
more freedom for the data modeler in implementing the data model.
For example, if the data model uses an object-oriented language,
such as Java, then the above structure enables all of the abstract
classes to be collapsed to a single concrete class. If this is
done, attributes as well as relationships are inherited.
4.3.1. SUPAPolicyObject
A SUPAPolicyObject serves as a single root of the SUPA system
(i.e., all other classes in the model are subclasses of the
SUPAPolicyObject class). This simplifes code generation and
reusability. It also enables SUPAPolicyMetadata objects to be
attached to any appropriate subclass of SUPAPolicyObject.
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4.3.2. SUPAPolicyStructure
SUPAPolicyStructure is an abstract superclass that is the base
class for defining different types of policies (however, in this
version of this document, only ECA policy rules are modeled). It
serves as a convenient aggregation point to define atomic (i.e.,
individual policies that can be used independently) and composite
(i.e., hierarchies of policies) SUPAPolicies; it also enables
PolicySources and/or PolicyTargets to be associated with a given
set of Policies.
SUPAPolicies are defined as either a stand-alone PolicyContainer
or a hierarchy of PolicyContainers. A PolicyContainer specifies
the structure, content, and optionally, source, target, and
metadata information for a SUPAPolicy. This is implemented by the
subclasses of SUPAPolicyStructure. For example, the composite
pattern is used to create two subclasses of the SUPAECAPolicyRule
class; SUPAECAPolicyRuleAtomic is used for stand-alone policies,
and SUPAECAPolicyRuleComposite is used to build hierarchies of
policies.
This document defines a SUPAPolicy as an ECA Policy Rule, though
the GPIM enables other types of policies to be defined and used
with an ECA policy rule. The GPIM model is used in [2] and [5],
along with extensions that allow [2] and [5] to define multiple
types of policies that are derived from the GPIM. They also allow
different combinations of different types of policy rules to be
used with each other. Most previous work cannot define different
types of policy rules; please see Appendix A for a comparison to
previous work.
4.3.3. SUPAPolicyComponentStructure
SUPAPolicyComponentStructure is an abstract superclass that is the
base class for defining components of different types of policies.
SUPAPolicyStructure subclasses define the structure of a policy,
while SUPAPolicyComponentStructure subclasses define the content
that is contained in the structure of a policy. For example, a
SUPAECAPolicyRule is an imperative policy rule, and defines its
structure; its event, condition, and action clauses are populated
by SUPAPolicyComponentStructure subclasses. The strength of this
design is that different types of policies (e.g., imperative and
declarative policies) can be represented using a common set of
policy components.
Please see Appendix for a comparison to previous work.
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4.3.4. SUPAPolicyClause
All policies derived from the GPIM are made up of one or more
SUPAPolicyClauses, which define the content of the Policy.
This enables a Policy of one type (e.g., ECA) to invoke Policies
of the same or different types. SUPAPolicyClause is an abstract
class, and serves as a convenient aggregation point for assembling
other objects that make up a SUPAPolicyClause.
The GPIM defines a single concrete subclass of SUPAPolicyClause,
called SUPAEncodedClause. This is a generic clause, and can be
used by any type of Policy in a stand-alone fashion. It can also
be used in conjunction with other SUPAPolicyClauses. The EPRIM
also defines a subclass of SUPAPolicyClause; see section 6.7).
The structure of the GPIM is meant to provide an extensible
framework for defining different types of policies. This is
demonstrated by the EPRIM (see section 6) and the LSIM (see the
Appendices) that each define new subclasses of SUPAPolicyClause
(i.e., SUPABooleanClause and SUPALogicClause, respectively)
without defining new classes that have no GPIM superclass.
A SUPAPolicyClause is defined as an object. Therefore, clauses and
sets of clauses are objects, which promotes reusability.
4.3.5. SUPAPolicyComponentDecorator
One of the problems in building a policy model is the tendency to
have a multitude of classes, and hence object instances, to
represent different combinations of policy events, conditions, and
actions. This can lead to class and/or relationship explosion.
Please see Appendix A for a comparison to previous work.
SUPAPolicyClauses are constructed using the Decorator Pattern
[11]. This is a design pattern that enables behavior to be
selectively added to an individual object, either statically or
dynamically, without affecting the behavior of other objects from
the same class. The decorator pattern uses composition, instead of
inheritance, to avoid class and relationship explosion. The
decorator pattern also enable new objects to be composed from
parts or all of existing objects without affecting the existing
objects.
This enables the resulting SUPAPolicyClause to be constructed
completely from objects in the SUPA information model. This
facilitates the construction of policies at runtime by a machine.
This is also true of [2] and [5]; however, this is NOT true of
most other models. Please see Appendix A for a comparison to
previous work.
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SUPAPolicyComponentDecorator defines four types of objects that
can be used to form a SUPAPolicyClause. Each object may be used
with all other objects, if desired. The first three are defined
in the GPIM, with the last defined in the EPRIM. The objects are:
o SUPAPolicyTerm, which enables a clause to be defined in a
canonical {variable, operator, value} form
o SUPAGenericDecoratedComponent, which enabled a custom object
to be defined and then used in a SUPAPolicyClause
o SUPAPolicyCollection, which enables a collection of objects
to be gathered together and associated with all or a portion
of a SUPAPolicyClause
o SUPAECAComponent, which defines Events, Conditions, and
Actions as reusable objects
This approach facilitates the machine-driven construction of
policies. Note that this is completely optional; policies do not
have to use these constructs.
4.3.6. SUPAPolicyTarget
A SUPAPolicyTarget is a set of managed entities that a SUPAPolicy
is applied to. A managed entity can only be designated a
SUPAPolicyTarget if it can process actions from a SUPAPolicy.
A managed object may not be in a state that enables management
operations to be performed on it. Furthermore, the policy-based
management system SHOULD ensure that the management entity
performing the management operations has the proper permissions to
perform the management operations. The design of the
SUPAPolicyTarget addresses both of these criteria.
4.3.7. SUPAPolicySource
A SUPAPolicySource is a set of managed entities that authored, or
are otherwise responsible for, this SUPAPolicy. Note that a
SUPAPolicySource does NOT evaluate or execute SUPAPolicies. Its
primary use is for auditability and the implementation of deontic
and/or alethic logic.
4.4. The Design of the GPIM
This section describes the overall design of the GPIM.
The GPIM defines a policy as a type of PolicyContainer. For this
version, only ECA Policy Rules will be described. However, it
should be noted that the mechanism described is applicable to
other types of policies (e.g., declarative) as well.
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4.4.1. Structure of Policies
Recall that a PolicyContainer was defined as a special type of
container that provides at least the following three functions:
1. It uses metadata to define how its content is described
and/or prescribed
2. It separates the content of the policy from the
representation of the policy
3. It provides a convenient control point for OAMP operations.
The first requirement is provided by the ability for any subclass
of Policy (the root of the information model) to aggregate one or
more concrete instances of a SUPAPolicyMetadata class. This is
explained in detail in section 5.2.2.
The second requirement is met by representing an ECA Policy as
having two parts: (1) a rule part and (2) components that make up
the rule. Since functional and declarative policies are not,
strictly speaking, "rules", the former is named PolicyStructure,
while the latter is named PolicyComponentStructure.
The third requirement is met by the concrete subclasses of
PolicyStructure. Since they are PolicyContainers, they are made
up of the SUPAECAPolicyRule, its commponents, and any metadata
that applies to the PolicyContainer, the SUPAECAPolicyRule, and.or
any components of the SUPAECAPolicyRule. This provides optional
low-level control over any part of the SUPAECAPolicyRule.
The above requirements result in the design shown in Figure 4.
A SUPAHasPolicyMetadata A
+------------------+/ \ \+--------------------+
| SUPAPolicyObject + A -----------------------+ SUPAPolicyMetadata |
+---------+--------+\ / /+--------------------+
/ \ 0..n 0..n
I
I
+------+------------------------------------+
I I
A I A I
+--------+------------+ +------------------+-----------+
| SUPAPolicyStructure | | SUPAPolicyComponentStructure |
+--------+------------+ +-------------+----------------+
/ \ / \
I I
I I
(subclasses representing (subclasses representing
different types of policies) different policy components)
Figure 4. Structure of a Policy
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Note that aggregation in Figure 4 (named SUPAHasPolicyMetadata)
is realized as an association class, in order to manage which set
of Metadata can be aggregated by which SUPAPolicyObject. The
combination of these three functions enables a PolicyContainer
to define the behavior of how its constituent components will be
accessed, queried, stored, retrieved, and how they operate.
It is often necessary to construct groups of policies. The GPIM
follows [2] and [5], and uses the composite pattern [11] to
implement this functionality, as shown in Figure 5 below. There
are a number of advantages to using the composite pattern over a
simple relationship, as detailed in [11].
Figure 5 shows that SUPAPolicyStructure has a single subclass,
called SUPAECAPolicyRule. Note, however, that other types of
policies, such as declarative policies, can be defined as
subclasses of SUPAPolicyStructure in the future.
A
+---------------------+
| SUPAPolicyStructure |
+--------+------------+
/ \
I
I
+---------------+----------------+
I I
C I A I
+----------------+---------------+ +-----------+-----------+
| Future Subclasses to Represent | | SUPAECAPolicyRule |
| Represent Different Policies | +-----------------------+
+--------------------------------+
Figure 5. The Composite Pattern Applied to SUPAPolicyStructure
4.4.2. Representing an ECA Policy Rule
An ECA policy rule is a 3-tuple, made up of one or more event
clauses, one or more condition clauses, and one or more action
clauses. Each clause may be viewed as a predicate, as it provides
a TRUE or FALSE output. The canonical form of a clause is a
3-tuple of the form "variable operator value", and can be made
into more complex Boolean expressions. For example, the
SUPAPolicyClause: "((A AND B) OR NOT (C AND D)) consists of two
clauses, "(A AND B)" and "(C OR D)", that are combined together
using the operators OR and NOT.
A SUPAECAPolicyRule is defined (in the EPRIM) as an abstract
subclass of SUPAPolicyStructure.
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A A
+---------------------------+ +------------------+
| SUPAPolicyStructure | | SUPAPolicyClause |
+---------+---------+-------+ +--------+----+----+
/ \ / \ 0..1 1..n / \ / \
I A | I
I \ / | I
I | | I
I | SUPAHasPolicyClause | I
I +------------------------+ I
A I A I
+------+------------+ +----------+-------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+-------------------+ +------------------+
Figure 6. SUPAECAPolicyRule Aggregating SUPAPolicyClauses
Note that the aggregation SUPAHasPolicyClause in Figure 6 is
realized as an association class, in order to manage which set
of SUPAPolicyClauses can be aggregated by which set of
SUPAECAPolicyRules. This aggregation is defined at the
SUPAPolicyStructure level, and not at the lower level of
SUPAECAPolicyRule, so that non-ECA policies can also use this
aggregation.
Since a SUPAECAPolicyRule consists of three SUPAPolicyClauses,
at least three separate instances of the SUPAHasPolicyClause
aggregation are instantiated in order to make a complete
SUPAECAPolicyRule, as shown in Figure 7.
A A
+-------------------+ +--------------------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+--+----+----+------+ +-------+----+----+--+
/ \ / \ / \ 1..n 0..n / \ / \ / \
A A A | | |
\ / \ / \ / | | |
| | | | | |
| | | SUPAHasPolicyClause #1 | | |
| | +------------------------------+ | |
| | | |
| | SUPAHasPolicyClause #2 | |
| +----------------------------------------+ |
| |
| SUPAHasPolicyClause #3 |
+--------------------------------------------------+
Figure 7. Instantiating a SUPAECAPolicyRule, part 1
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In figure 7, SUPAECAPolicyRule is shown as "owning" these three
aggregations, since it inherits them from its superclass
(SUPAPolicyStructure). The three aggregations represent the
event, condition, and action clauses of a SUPAECAPolicyRule.
Note that each of these clauses MAY consist of one or more
SUPAPolicyClauses. Similarly, each SUPAPolicyClause MAY consist
of one or more predicates. In this way, complex event, condition,
and action clauses, which are combinations of Boolean expressions
that form a logical predicate) are supported, without having to
define additonal objects (as is done in previous work; please
see Appendix A for a comparison to previous work.
The multiplicity of the SUPAHasPolicyClause aggregation is
0..n on the aggregate side and 1..n on the part side. This means
that a particular SUPAECAPolicyRule MUST aggregate at least one
SUPAPolicyClause, and that a given SUPAPolicyClause MAY be
aggregated by zero or more SUPAECAPolicyRule objects.
This cardinality MAY be refined to 3..n for SUPAECAPolicyRules,
since a SUPAECAPolicyRule MUST have at least three separate clauses.
However, since a SUPAPolicyStructure is the owner of this
aggregation (which is inherited by SUPAECAPolicyRule), the
cardinality is defined to be 1..n on the part side because other
types of Policies have different needs. The 0..n cardinality
means that a SUPAPolicyClause may be aggregated by zero or more
SUPAECAPolicyRules. The zero is provided so that SUPAPolicyClauses
can be stored in (for example) a repository before the
SUPAECAPolicyRule is created; the "or more" recognizes the fact
that multiple SUPAECAPolicyRules could aggregate the same
SUPAPolicyClause.
In Figure 7, suppose that SUPAHasPolicyClause#1, #2, and #3
represent the aggregations for the event, condition, and action
clauses, respectively. This means that each of these
SUPAHasPolicyClause aggregations must explicitly identify the
type of clause that it represents.
In looking at Figure 7, there is no difference between any of the
three aggregations, except for the type of clause that the
aggregation represents (i.e., event, condition, or action clause).
Therefore, three different aggregations, each with their own
association class, is not needed. Instead, the GPIM defines a
single aggregation (SUPAHasPolicyClause) that is realized using a
(single) abstract association class (SUPAHasPolicyClauseDetail);
this association class is then subclassed into three concrete
subclasses, one each to represent the semantics for an event,
condition, and action clause.
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The policy management system may use any number of different
software mechanisms, such as introspection or reflection, to
determine the nature of the aggregation (i.e., what object types
are being aggregated) in order to select the appropriate subclass
of SUPAHasPolicyClauseDetail. The three subclasses of
SUPAHasPolicyClauseDetail are named SUPAHasPolicyEventDetail,
SUPAHasPolicyConditionDetail, and SUPAHasPolicyActionDetail,
respectively. While Event, Condition, and Action objects are
typically used in ECA policy rules, the design in this document
enables them to be used as policy components of other types of
policies as well. This is shown in Figure 8.
A A
+-------------------+ +------------------+
| SUPAECAPolicyRule | | SUPAPolicyClause |
+---------+---------+ +----------+-------+
/ \ 1..n 0..n / \
A |
\ / |
| |
| SUPAHasPolicyClause |
+--------------+-----------------+
^
|
A |
+--------------+------------+
| SUPAHasPolicyClauseDetail |
+--------------+------------+
/ \
I
I
+----------------+-----------------------+
I I I
C I C I C I
+--------+-----+ +-------+----------+ +---------+-----+
|Event subclass| |Condition subclass| |Action subclass|
+--------------+ +------------------+ +---------------+
Figure 8. Instantiating a SUPAECAPolicyRule, part 2
4.4.3. Creating SUPA Policy Clauses
There are two different types of Policy Components. They are a
SUPAPolicyClause and a SUPAPolicyComponentDecorator. The former
is used to construct SUPAECAPolicyRules, while the latter is used
to add behavior to a SUPAPolicyClause. This enables the structure
and capabilities of the SUPAPolicyClause to be adjusted
dynamically at runtime.
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However, since each SUPAECAPolicyRule can be made up of a variable
number of SUPAPolicyComponents, the decorator pattern is used to
"wrap" any concrete subclass of SUPAPolicyClause with zero or more
concrete subclasses of the PolicyComponentDecorator object. This
avoids problems of earlier models that resulted in a proliferation
of classes and relationships.
Figure 9 shows these two class subclasses. Note that the decorator
pattern [11] is used to enable subclasses of the
SUPAPolicyComponentDecorator class to add their attributes and/or
behavior to a SUPAPolicyClause (as stated in section 4.3) without
affecting the behavior of other objects from the same class. More
specifically, concrete subclasses of the (abstract)
SUPAPolicyComponentDecorator class can be used to decorate, or
"wrap", any of the concrete subclasses of the (abstract)
SUPAPolicyClause class.
A
+------------------------------+ 1..n
| SUPAPolicyComponentStructure +----------------------+
+----------------+-------------+ |
/ \ |
I SUPAHasPolicyComponentDecorators |
I |
+--------------+-----------+ |
I I |
A I A I |
+---------+--------+ +--------------+---------------+ 0..1 |
| | | |/ \ |
| SUPAPolicyClause | | SUPAPolicyComponentDecorator + A -----+
| | | |\ /
+------------------+ +------------------------------+
Figure 9. Subclasses of SUPAPolicyComponentStructure
Instead of using inheritance to statically create new classes to
represent new types of objects, the decorator pattern uses
composition to dynamically combine attributes and behavior from
existing objects into new objects. This is done by defining an
interface in SUPAPolicyComponent that all of the subclasses of
SUPAPolicyComponent conform to. Since the subclasses are of the
same type as SUPAPolicyComponent, they all have the same interface.
This allows each concrete SUPAPolicyComponentDecorator subclass to
add its attributes and/or behavior to the concrete subclass of
SUPAPolicyClause that it is decorating (or "wrapping").
This represents an important design optimization for data models.
Note that a single SUPAECAPolicyRule can consist of any number of
SUPAPolicyClauses, each of very different types. If inheritance
was used, then a subclass AND an aggregation would be required for
each separate clause that makes up the policy rule.
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Clearly, continuing to create subclasses is not practical. Worse,
suppose composite objects are desired (e.g., a new object Foo is
made up of existing objects Bar and Baz). If all that was needed
was one attribute of Bar and two of Baz, the developer would still
have to use the entire Bar and Baz classes. This is wasteful and
inefficient. In contrast, the decorator pattern enables all, or
just some, of the attributes and/or behavior of a class to "wrap"
another class. This is used heavily in many production systems
(e.g., the java.io package) because the result is only the
behavior that is required, and no other objects are affected.
The SUPAPolicyComponentDecorator class hierarchy is used to define
objects that may be used to construct a SUPAPolicyClause. The
decorator object can add behavior before, and/or after, it
delegates to the object that it is decorating. The subclasses of
SUPAPolicyComponentDecorator provide a very flexible and completely
dynamic mechanism to:
1) add or remove behavior to/from an object
2) ensure that objects are constructed using the minimum amount
of features and functionality required
SUPAPolicyComponentDecorator defines four subclasses, as shown in
Figure 10.
A
+------------------------------+
| SUPAPolicyComponentDecorator |
+--------------+---------------+
/ \
I
I
I
+------------+-------------+----------------+
I I I I
A I I C I I
+--------+-------+ I +---------+------------+ I
| SUPAPolicyTerm | I | SUPAPolicyCollection | I
+----------------+ I +----------------------+ I
(for defining I (for defining sets and/or I
clauses in I groups of objects) I
canonical form) I I
I I
C I A I
+----------------+--------------+ +---------+--------+
| SUPAGenericDecoratedComponent | | SUPAECAComponent |
+-------------------------------+ +------------------+
(for decorating concrete (for defiing reusable
subclasses of SUPAPolicyClause) event, condition,
and action objects)
Figure 10. Subclasses of SUPAPolicyComponentDecorator
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If a SUPAEncodedClause is being used, then there is no need to
use any of the SUPAPolicyComponentDecorator subclasses, since
the SUPAEncodedClause already completely defines the content of
the SUPAPolicyClause.
However, if a SUPAEncodedClause is NOT being used, then a
SUPAPolicyClause will be constructed using one or more types of
objects that are each subclasses of SUPAPolicyComponentDecorator.
These four subclasses provide four different ways to construct a
SUPAPolicyClause:
1) SUPAPolicyTerm: as a {variable, operator, value} clause
2) SUPAEncodedClause: as an encoded object (e.g., to pass YANG
or CLI code)
3) SUPAPolicyCollection: as a collection of objects that
requires further processing in order to be made into a
SUPAPolicyClause
4) SUPAECAComponent: subclasses define reusable Event,
Condition, or Action objects
These four different types of objects can be intermixed. For
example, the first and last types can be combined as follows:
Variable == Event.baz (A)
Condition BETWEEN VALUE1 and VALUE2 (B)
(Event.severity == 'Critical' AND
(SLA.violation == TRUE OR User.class == 'Gold')) (C)
In the above rules, (A) uses Event.baz to refer to an attribute
of the Event class; (B) defines two different instances of a Value
class, denoted as Value1 and Value2; (C) uses the nomenclature
foo.bar, where foo is the name of a class, and bar is the name of
an attribute of that class.
4.4.4. Creating SUPAPolicyClauses
The GPIM defines a single subclass of SUPAPolicyClause, called
SUPAEncodedClause. This clause is generic in nature, and MAY be
used with any type of policy (ECA or otherwise). The EPRIM
defines an ECA-specific subclass of the GPIM, called a
SUPABooleanClause, which is intended to be used with just
ECA policy rules; however, other uses are also possible.
Together, the GPIM and EPRIM provide several alternatives to
implement a SUPAPolicyClause, enabling the developer to
optimize the solution for different constraints:
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1) The SUPAPolicyClause can be encoded using one or more
SUPAEncodedClauses; a SUPAEncodedClause encodes the
entire content of its respective event, condition, or
action clause.
2) The SUPAPolicyClause can be defined using one or more
SUPABooleanClauses; each of the three clauses can be
defined as either a single SUPABooleanClause, or a
combination of SUPABooleanClauses that are logically
ANDed, ORed, and/or NOTed.
3) The above two mechanisms can be combined (e.g., the first
used to define the event clause, and the second used to
define the condition and action clauses).
Figure 11 shows the subclasses of SUPAPolicyClause.
A
+------------------+
| SUPAPolicyClause |
+--------+---------+
/ \
I
I
I
+---------------+-------------+
I I
A I C I
+--------+----------+ +----------+--------+
| SUPABooleanClause | | SUPAEncodedClause |
+-------------------+ +-------------------+
Figure 11. Subclasses of SUPAPolicyClause
SUPABooleanClause is defined in the EPRIM, and is used to
construct Boolean clauses that collectively make up a
SUPAPolicyClause. It is abstract, so that the composite pattern
can be applied to it, which enables hierarchies of Boolean
clauses to be created. SUPAEncodedClause (see section 6.7) is
used to encode the content of a SUPAPolicyClause as an attribute
(instead of reusable objects).
4.4.5. SUPAPolicySources
A SUPAPolicySource is a set of managed entities that authored,
or are otherwise responsible for, this SUPAPolicy. Note that a
SUPAPolicySource does NOT evaluate or execute SUPAPolicies. Its
primary use is for auditability, authorization policies, and
other applications of deontic and/or alethic logic.
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SUPAPolicyStructure defines four relationships. Two of these
(SUPAHasPolicySource and SUPAHasPolicyTarget), which are both
aggregations, relate a SUPAPolicyStructure to a SUPAPolicySource
and a SUPAPolicyTarget, respectively. Since SUPAECAPolicyRule is
a subclass of SUPAPolicyStructure, it (and its subclasses) inherit
both of these aggregations. This enables SUPAPolicySources and/or
SUPAPolicyTargets to be attached to SUPAECAPolicyRules (but NOT to
components of a SUPAPolicy).
Figure 12 shows how SUPAPolicySources and SUPAPolicyTargets are
attached to a SUPAPolicy. Note that both of these aggregations
are defined as optional, since their multiplicity is 0..n - 0..n.
In addition, both of these aggregations are realized as
association classes, in order to be able to control which
SUPAPolicySources and SUPAPolicyTargets are attached to a given
SUPAECAPolicyRule.
A
+------------------+
| SUPAPolicyObject |
+--------+---------+
/ \
I
I
I
+--------------+-----+---------------------+
I I I
A I C I C I
+-----------+---------+ +-------+--------+ +--------+-------+
| SUPAPolicyStructure | |SUPAPolicySource| |SUPAPolicyTarget|
+------+-------+------+ +----------+-----+ +----------+-----+
0..n / \ / \ 0..n 0..n / \ 0..n / \
A A | |
\ / \ / | |
| | | |
| | | |
| +--------------------+ |
| SUPAHasPolicySource |
| |
+-------------------------------------------------+
SUPAHasPolicyTarget
Figure 12. ECAPolicyRules, SUPAPolicySources, and PolicyTargets
A SUPAPolicySource MAY be mapped to a role (e.g., using the
role-object pattern [11]); this indirection makes the system less
fragile, as entities can be transparently added or removed from
the role definition without adversely affecting the definition of
the SUPAPolicy. Note that SUPAPolicyRole is a subclass of
SUPAPolicyMetadata.
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4.4.6. SUPAPolicyTargets
A SUPAPolicyTarget defines the set of managed entities that a
SUPAPolicy is applied to. This is useful for debugging, as well as
when the nature of the application requires the set of managed
entities affected by a Policy to be explicitly identified. This is
determined by two conditions:
1) The set of managed entities that are to be affected by the
SUPAPolicy must all agree to play the role of a
SUPAPolicyTarget. For example, a managed entity may not be
in a state that enables SUPAPolicies to be applied to it;
hence, in this case, it MUST NOT assume the role of ability
SUPAPolicyTarget
2) A SUPAPolicyTarget must be able to:
a) process (either directly or with the aid of a proxy)
SUPAPolicies, or
b) receive the results of a processed SUPAPolicy and
apply those results to itself.
Figure 12 showed how SUPAPolicyTargets are attached to
SUPAECAPolicyRules.
A SUPAPolicyTarget MAY be mapped to a role (e.g., using the
role-object pattern [11]); this indirection makes the system less
fragile, as entities can be transparently added or removed from
the role definition without adversely affecting the definition of
the SUPAPolicy. Note that SUPAPolicyRole is a subclass of
SUPAPolicyMetadata.
4.4.7. Policy Metadata
Metadata is, literally, data about data. As such, it can be
descriptive or prescriptive in nature.
4.4.7.1. Motivation
There is a tendency in class design to make certain attributes,
such as description, status, validFor, and so forth, bound to a
specific class (e.g., [6]). This is bad practice in an information
model. For example, different classes in different parts of the
class hierarchy could require the use of any of these attributes;
if one class is not a subclass of the other, then they must each
define the same attribute as part of their class structure. This
makes it difficult to find all instances of the attribute and
ensure that they are synchronized. Furthermore, context can
dynamically change the status of an object, so an easy way to
update the status of one object instance without affecting other
instances of the same object is required.
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Many models, such as [4] and [6], take a simplistic approach of
defining a common attribute high in the hierarchy, and making it
optional. This violates classification theory, and defeats the
purpose of an information model, which is to specify the
differences in characteristics and behavior between classes (as
well as define how different classes are related to each other).
Note that this also violates a number of well-known software
architecture principles, including:
o the Liskov Substitution Principle [13]
(if A is a subclass of B, then objects instantiated from
class B may be replaced with objects instantiated from
class A WITHOUT ALTERING ANY OF THE PROGRAM SEMANTICS)
o the Single Responsibility Principle [14]
(every class should have responsibility over one, and only
one, part of the functionality provided by the program)
Most models use inheritance, not composition. The former is
simpler, but has some well-known problems. One is called "weak
encapsulaton", meaning that a subclass can use attributes and
methods of a superclass, but if the superclass changes, the
subclass may break. Another is that each time a new object is
required, a new subclass must be created. These problems are
present in [RFC3460], [4], and [6].
Composition is an alternative that provides code that is easier to
use. This means that composition can provide data models that are
more resistant to change and easier to use. By using composition,
we can select just the metadata objects that are needed, instead
of having to rely on statically defined objects. We can even
create new objects from a set of existing objects through
composition. Finally, we can use the decorator pattern to select
just the attributes and behaviors that are required for a given
instance.
In [2] and [5], a separate metadata class hierarchy is defined to
address this problem. This document follows this approach.
4.4.7.2. Design Approach
The goal of the GPIM is to enable metadata to be attached to any
subclass of SUPAPolicyObject that requires it. Since this is a
system intended for policy-based management, it therefore makes
sense to be able to control which metadata is attached to which
policies dynamically (i.e., at runtime).
One solution is to use the Policy Pattern [1], [2], [6], [12].
This pattern was built to work with management systems whose
actions were dependent upon context. The Policy Pattern works as
follows:
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o Context is derived from all applicable system inputs (e.g.,
OAMP data from network elements, business goals, time of
day, geo-location, etc.).
o Context is then used to select a working set of Policies.
o Policies are then used to define behavior at various
control points in the system.
o One simple type of control point is an association class.
Since the association class represents the semantics of how
two classes are related to each other, then
o ECAPolicyRule actions can be used to change the attribute
values, methods, and relationships of the association
class
o This has the affect of changing how the two classes are
related to each other
o Finally, as context changes, the working set of policies
change, enabling the behavior to be adjusted to follow
changes in context (according to appropriate business goals
and other factors, of course) in a closed loop manner.
Conceptually, this is accomplished as shown in Figure 13 below.
Defines
+----------+ Behavior +------------+
| Policies +----------------+ | SUPAPolicy |
+----+-----+ 1..n | +------+-----+
0..n / \ | / \ 0..n
| | A
| | \ /
| 1..n \ / |
| +-----------+--------------+ |
| | SUPAPolicyMetadataDetail | |
| +-----------+--------------+ |
| | |
| Selects | |
| Policies | |
| | |
| +-------------------->+
| Applies |
/ \ Behavior |
A |
0..n \ / \ / 0..n
+----+-----+ +--------+---------+
| Context | |SUPAPolicyMetadata|
+----------+ +------------------+
Figure 13. Context-Aware Policy Rules
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4.4.7.2.1. Policies and Actors
The Policy Continuum ([1] [5] [10] [12]) was defined to associate
different actors with different policies at different levels of
business and/or technical specificity. Context-aware policy rules,
and the Policy Pattern, were defined to realize this association.
Four important functions related to the lifecycle of policies are
design, implementation, deployment, and execution. There are many
different possible definitions of these functions (even for policy
lifecycle management); however, for the purposes of this document,
they are defined as follows:
o Design: The process of defining a software architecture
to satisfy user requirements.
o Development: the process of documenting, programming,
testing, and maintaining code and applications
as part of a software product
o Deployment: the process that assembles and transfers
completed software artifacts to a state that
enables their execution
o Execution: the process of installing, activating, running,
and subsequently deactivating executable
software products
The design process is responsible for producing a software
architecture. This emphasizes the design, as opposed to the
programming, of software systems. In contrast to design,
development emphasizes constructing software artifacts via coding
and documentation.
Deployment may be described as the process of releasing software.
It includes all of the operations required to assemble a completed
software product. It typically also includes the process of
preparing a software product for execution (e.g., assembling a set
of software products into a larger product, determining if the
consumer site has appropriate resources to install and execute the
software product, and collecting information on the feasbility of
using the software product). This contrasts with the execution
process, which is the set of processes that follow deployment.
In summary, exemplar states in the policy lifecycle process
include:
o Design: determining how the policy-based management
system will operate
o Development: documenting, programming, testing, and
maintaining policies and policy components
o Deployment: assembling the components of a policy-based
management system
o Execution: installing, enabling, running, disabling,
and uninstalling policies and policy components
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4.4.7.2.2. Deployment vs. Execution of Policies
One of the primary reasons for separating the deployment and
execution processes is to differentiate between environments that
are not ready to execute policies (i.e., deployment) and
environments that are ready to execute policies (i.e., execution).
This is an important consideration, since policies that are
related to the same set of tasks may be deployed in many different
places (e.g., in a policy system vs. in a network device). In
addition, each managed entity in the set of SUPAPolicyTargets may
or may not be in a state that allows SUPAPolicies to be applied to
it (see section 4.4.6.).
Hence, this design includes dedicated class attributes for
getting and setting the deployment and execution status, as well
as enabling and disabling, SUPAPolicies (see section 5.3.1.).
4.4.7.2.3. Using SUPAMetadata for Policy Deployment and Execution
One way of encoding deployment and execution status for policies
and policy components is to attach Metadata objects to affected
SUPAPolicyStructure and SUPAPolicyComponentStructure objects.
This provides an extensible and efficient means to describe
and/or prescribe deployment and/or execution status of a policy
or a policy component. It is extensible, since classes and
relationships can be used, as opposed to a set of attributes. It
is efficient, because the decorator pattern (see section 5.7) is
used (this enables attributes and/or methods of objects, or the
entire object, to be used to add characteristics and/or behavior
to a given object.
SUPAPolicyMetadata objects (see sections 5.16 - 5.20) may be
attached to the SUPAECAPolicyRule and/or any of its components
to define additional semantics of the SUPAECAPolicyRule. For
example, SUPAAccessMetadataDef (see section 5.19) and/or
SUPAVersionMetadataDef (see section 5.20) may be attached to
define the access privileges and version information,
respectively, of a policy rule and/or its components.
The SUPAPolicyStructure contains two attributes,
supaPolDeployStatus and supaPolExecStatus (see sections 5.3.1.3.
and 5.3.1.4., respectively) that SUPAPolicyMetadata objects can
use to get and set the deployment and execution status of a
SUPAPolicy. This allows metadata to be used to alter the
deployment and/or execution state of a policy (or a set of
policy components) without having to affect other parts of the
policy-based management system. The supaPolDeployStatus attribute
indicates that this SUPAPolicy can or cannot be deployed. If it
cannot be deployed. Similarly, the supaPolExecStatus attribute
is used to indicate if a particular SUPAPolicy has executed, is
currently executing, or is ready to execute, and whether or not
the execution of that SUPAPolicy had any failures.
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The reverse is also true (and hence, forms a closed-loop system
controlled by metadata). For example, if the set of deployed
SUPAPolicies are SUPAECAPolicyRules, then when the actions of
these SUPAECAPolicyRules are executed, the overall context has
changed (see section 4.4.7.2). The context manager could then
change attribute values (directly or indirectly) in the
SUPAPolicyMetadataDetail association class. This class represents
the behavior of the SUPAHasPolicyMetadata aggregation, which is
used to define which SUPAPolicyMetadata can be attached to which
SUPAPolicy objet in this particular context. For example, the
access privileges of a policy and/or policy component could be
changed dynamically, according to changes in context.
By using the decorator pattern on SUPAPolicyMetadata, any number
of SUPAPolicyMetadata objects (or their attributes, etc.) can be
wrapped around a concrete subclass of SUPAPolicyMetadata. This is
shown in Figure 14 below.
4.4.7.3. Structure of SUPAPolicyMetadata
SUPAPolicyMetadata also uses the decorator pattern to provide an
extensible framework for defining metadata to attach to SUPAPolicy
subclasses. Its two principal subclasses are
SUPAPolicyConcreteMetadata and SUPAPolicyMetadataDecorator. The
former is used to define concrete subclasses of SUPAPolicyMetadata
that are attached at runtime to SUPAPolicy subclasses, while the
latter is used to define concrete objects that represent reusable
attributes, methods, and relationships that can be added to
subclasses of SUPAPolicyConcreteMetadata.
For example, concepts like identification, access control, and
version information are too complex to represent as a single
attribute, or even a couple of attributes - they require the
generic power of objects to represent their characteristics and
behavior. Furthermore, defining concrete classes to represent
these concepts in the policy hierarchy is fragile, because:
1. not all objects that use these concepts need all of the
information represented by them (e.g., two subclasses of an
Identification Object may be Passport and Certificate, but
these two objects are rarely used together, and even those
contexts that use one of these classes may not need all of
the data in that class)
2. defining a class means defining its attributes, methods, and
relationships at a particular place in the hierarchy; this
means that defining a relationship between a class A and
another class B SHOULD only be done if all of the subclasses
of B can use the attributes, methods, and relationships of A
(e.g., in the above example, defining a relationship between
an Identification Object and a superclass of a router class
is not appropriate, since routers do not use Passports)
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A
+------------------+
| SUPAPolicyObject |
+--------+---------+
/ \ 0..n
A
\ /
| A
| 0..n +--------------------+
| SUPAHasPolicyMetadata \| |
+-------------+-----------------+ SUPAPolicyMetadata |
^ /| |
| +------+------+------+
A | / \ | 1..n
+-------------+---------------+ I |
1..n | | I |
+----------+ SUPAHasPolicyMetadataDetail | I |
| | | I |
| +-----------------------------+ I |
| I |
| (gets/sets values of attributes and/or I |
| methods of the SUPAHasPolicyMetadataDetail I |
| class; this affects which SUPAPolicyMetadata I |
| objects can be attached to which policies I |
| and policy components) I |
| I |
| C I |
| +----------------------------+ I |
| | | I |
+----------+ SUPAPolicyConcreteMetadata +IIIIIIIII+ |
| | I |
+----------------------------+ I |
I |
A I |
+-----------------------------+ I |
| | I |
| SUPAPolicyMetadataDecorator +IIIIIIIII+ |
| | |
+-------+--------------+------+ |
/ \ / \ 0..1 |
I A |
I \ / |
I | |
subclasses for adding | |
behavior to policies +-----------------------+
and policy components PolicyObjectHasMetadata
Figure 14. SUPAPolicyMetadata Subclasses and Relationships
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Since a class encapsulates attributes, methods, and behavior,
defining the Identification Object in the above example as a type
of SUPAPolicyMetadata object enables the decorator pattern to be
used to attach all or part of that object to other objects that
need it.
Figure 15 shows a portion of the SUPAPolicyMetadata hierarchy.
A
+--------------------+
| | HasSUPAMetadataDecorator
| SUPAPolicyMetadata +-------------------+
| | 1..n |
+---------+----------+ |
I |
I |
I |
+-------------+-----------------+ |
| | |
C | | / \
+---------+------------------+ | A
| SUPAPolicyConcreteMetadata | A | 0..1 \ /
+----------------------------+ +--------+------------+-------+
| SUPAPolicyMetadataDecorator |
+------------+----------------+
I
+------------------------------+--------+
I I
I I
C I C I
+---------------+-------------+ +---------------------+--------+
| SUPAPolicyAccessMetadataDef | | SUPAPolicyVersionMetadataDef |
+-----------------------------+ +------------------------------+
Figure 15. SUPAPolicyMetadata Subclasses and Relationships
Figure 15 shows a relevant portion of the SUPAPolicyMetadata
hierarchy. SUPAPolicyConcreteMetadata is a concrete class that
subclasses of the SUPAPolicyMetadataDecorator class can wrap.
Two such subclasses, SUPAPolicyAccessMetadataDef and
SUPAPolicyVersionMetadataDef, are shown in Figure 15. This
enables access control and version information to be added
statically (at design time) or dynamically (at runtime) to
SUPAPolicyConcreteMetadata; this enables metadata-driven systems
to adjust the behavior of the management system to changes in
context, business rules, services given to end-users, and other
similar factors. This is discussed more in sections 5.18 - 5.20.
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4.5. Advanced Features
This section will be completed in the next revision of this
document.
4.5.1. Policy Grouping
This section will be completed in the next revision of this
document.
4.5.2. Policy Rule Nesting
This section will be completed in the next revision of this
document.
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5. GPIM Model
This section defines the classes, attributes, and relationships of
the GPIM.
5.1. Overview
The overall class hierarchy is shown in Figure 16; section numbers
are appended after each class.
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicyObject (5.2)
| |
| +---SUPAPolicyStructure (5.3)
| |
| +---SUPAPolicyComponentStructure (5.4)
| | |
| | +---SUPAPolicyClause (5.5)
| | | |
| | | +---SUPAEncodedClause (5.6)
| | |
| | +---SUPAPolicyComponentDecorator (5.7)
| | |
| | +---SUPAPolicyTerm (5.8)
| | | |
| | | +---SUPAPolicyVariable (5.9)
| | | |
| | | +---SUPAPolicyOperator (5.10)
| | | |
| | | +---SUPAPolicyValue (5.11)
| | |
| | +---SUPAGenericDecoratedComponent (5.12)
| | |
| | +---SUPAPolicyCollection (5.13)
| |
| +---SUPAPolicySource (5.14)
| |
| +---SUPAPolicyTarget (5.15)
|
+---SUPAPolicyMetadata (5.16)
|
+---SUPAPolicyConcreteMetadata (5.17)
|
+---SUPAPolicyMetadataDecorator (5.18)
|
+---SUPAPolicyAccessMetadataDef (5.19)
|
+---SUPAPolicyVersionMetadataDef (5.20)
Figure 16: Main Classes of the GPIM
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SUPAPolicy is the root of the SUPA class hierarchy. For
implementations, it is assumed that SUPAPolicy is subclassed from
a class from another model.
Classes, attributes, and relationships that are marked as
"mandatory" MUST be part of a conformant implementation (i.e., a
schema MUST contain these entities). This does not mean that these
entities must be instantiated; rather it means that they must be
able to be instantiated. Classes, attributes, and relationships
that are marked as "optional" MAY be part of a conformant
implementation.
Unless otherwise stated, all classes (and attributes) defined in
this section were abstracted from DEN-ng [2], and a version of
them are in the process of being added to [5]. However, the work
in [5] has been put on hold, and the names of many of the classes,
attributes, and relationships are slightly different.
5.2. The Abstract Class "SUPAPolicyObject"
This is a mandatory abstract class. Figure 17 shows the
SUPAPolicyObject class, and its four subclasses.
A 0..n 0..n A
+----------------+/ \ \+------------------+
|SUPAPolicyObject+ A ------------------------+SUPAPolicyMetadata|
+--------+-------+\ / SUPAHasPolicyMetadata /+------------------+
/ \
I
I
+-----------------+----------------+-----------+
I I I I
A I I I I
+--------+------------+ I I I
| SUPAPolicyStructure | I I I
+---------------------+ I I I
A I I I
+-----------------+------------+ I I
| SUPAPolicyComponentStructure | I I
+------------------------------+ I I
C I I
+---------+--------+ I
| SUPAPolicyTarget | I
+------------------+ I
C I
+----------+-------+
| SUPAPolicySource |
+------------------+
Figure 17. SUPAPolicyObject and Its Subclasses
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This class is the root of the SUPA class hierarchy. It defines the
common attributes and relationships that all SUPA subclasses
inherit.
A SUPAPolicyObject MAY be qualified by a set of zero or more
SUPAPolicyMetadata objects. This is provided by the
SUPAHasPolicyMetadata aggregation (see Section 5.2.2). This
enables the semantics of the SUPAPolicyObject to be more
completely specified.
5.2.1. SUPAPolicyObject Attributes
This section defines the attributes of the SUPAPolicyObject class.
These attributes are inherited by all subclasses of the GPIM
except for the SUPAPolicyMetadata class, which is a sibling class.
5.2.1.1. Object Identifiers
This document defines two class attributes in SUPAPolicyObject,
called supaPolObjIDContent and supaPolObjIDEncoding, that together
define a unique object ID. This enables all class instances to be
uniquely identified.
One of the goals of SUPA is to be able to generate different data
models that support different types of protocols and repositories.
This means that the notion of an object ID must be generic. It is
inappropriate to use data modeling concepts, such as keys, GUIDs,
UUIDs, FQDNs, URIs, and other similar mechanisms, to define the
structure of an information model. Therefore, a synthetic object
ID is defined using these two attributes. This can be used to
facilitate mapping to different data model object schemes, such
as those depending on URIs, FQDNs, UUIDs, primary key-foreign key
relationships, UUIDs, and others can all be accommodated.
The two attributes work together, with the supaPolObjIDContent
attribute defining the content of the object ID and the
supaPolObjIDEncoding attribute defining how to interpret the
content. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of an object
identifier for the object instance of this class.
Similarly, all SUPA classes are attributes are both uniquely
named as well as prepended with the prefixes "SUPA" and "supa",
respectively, to facilitate model integration.
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5.2.1.2. The Attribute "supaPolObjIDContent"
This is a mandatory string attribute that represents part of the
object identifier of an instance of this class. It defines the
content of the object identifier. It works with another class
attribute, called supaPolObjIDEncoding, which defines how to
interpret this attribute. These two attributes form a tuple,
and together enable a machine to understand the syntax and value
of an object identifier for the object instance of this class.
This is based on the DEN-ng class design [2].
5.2.1.3. The Attribute "supaPolObjIDEncoding"
This is a mandatory non-zero enumerated integer attribute that
represents part of the object identifier of an instance of this
class. It defines the format of the object identifier. It works
with another class attribute, called supaPolObjIDContent, which
defines the content of the object ID. These two attributes form
a tuple, and together enable a machine to understand the syntax
and value of an object identifier for the object instance of
this class. The supaPolObjIDEncoding attribute is mapped to the
following values:
0: undefined
1: GUID
2: UUID
3: primary key
4: foreign key
5: URI
6: FQDN
The value 0 may be used to initialize the system, or to signal
that there is a problem with this particular SUPAPolicyObject.
5.2.1.4. The Attribute "supaPolicyDescription"
This is an optional string attribute that defines a free-form
textual description of this object.
5.2.1.5. The Attribute "supaPolicyName"
This is an optional string attribute that defines the name of this
Policy. This enables any existing generic naming attribute to be
used for generic naming, while allowing this attribute to be used
to name Policy entities in a common manner. Note that this is NOT
the same as the commonName attribute of the Policy class defined
in [RFC3060], as that attribute is intended to be used with just
X.500 cn attributes.
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5.2.2. SUPAPolicyObject Relationships
The SUPAPolicyObject class currently defines a single relationship,
as defined in the subsections below.
5.2.2.1. The Aggregation "SUPAHasPolicyMetadata"
This is a mandatory aggregation that defines the set of
SUPAPolicyMetadata that are aggregated by this particular
SUPAPolicyObject. This aggregation is defined in section
5.16.2.
5.2.2.2. The Association Class "SUPAHasPolicyMetadataDetail"
This is a mandatory concrete association class that defines the
semantics of the SUPAPolicyMetadata aggregation. This enables the
attributes and relationships of the SUPAPolicyMetadataDetail class
to be used to constrain which SUPAPolicyMetadata objects can be
aggregated by this particular SUPAPolicyObject instance. This
association class is defined in Section 5.16.3.
5.3. The Abstract Class "SUPAPolicyStructure"
This is a mandatory abstract class that is used to represent the
structure of a SUPAPolicy. This class (and all of its subclasses)
is a type of PolicyContainer. SUPAPolicyStructure was abstracted
from DEN-ng [2], and a version of this class is in the process of
being added to [5]. However, the version in [5] differs
significantly. First, the class and relationship definitions ared
different. Second, [5] uses the composite pattern. Neither of
these are implemented in this document because of optimizations
done to the SUPA class hierarchy that are NOT present in [5].
For this release, the only official type of policy that is
supported is the event-condition-action (ECA) type of policy rule.
However, the structure of the SUPA hierarchy is defined to
facilitate adding new types of rules later.
A SUPAPolicy may take the form of an individual policy or a set
of policies. This requirement is supported by applying the
composite pattern to subclasses of the SUPAPolicyStructure class,
as shown in Figure 5. In this document, this is done for the
SUPAECAPolicyRule subclass, and results in two subclasses:
SUPAECAPolicyRuleAtomic (for defining stand-alone policies) and
SUPAECAPolicyRuleComposite (for defining hierarchies of policies).
Note that there is no need for a "match strategy attribute" that
some models [RFC3460], [4], [6] have; this is because the
SUPAPolicyStructure class is used just for containment. Hence, the
containers themselves serve as the scoping component for nested
policies.
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5.3.1. SUPAPolicyStructure Attributes
The following subsections define the attributes of the
SUPAPolicyStructure class.
The SUPAPolicyStructure class has a number of attributes that have
no counterpart in the SUPAPolicyComponentStructure class. This is
because these attributes are only appropriate at the level of a
policy rule, not at the level of a policy component.
Care must be taken in adding attributes to this class,
because the behavior of future subclasses of this class (e.g.,
declarative and functional policies) is very different than the
behavior of SUPAECAPolicyRules.
5.3.1.1. The Attribute "supaPolAdminStatus"
This is an optional attribute, which is an enumerated non-negative
integer. It defines the current administrative status of this
SUPAPolicyClause.
This attribute can be used to place this particular
SUPAPolicyStructure object instance into a specific administrative
state, such as enabled, disabled, or in test. Values include:
0: Unknown (an error state)
1: Enabled
2: Disabled
3: In Test (i.e., no operational traffic can be passed)
Value 0 denotes an error that prevents this SUPAPolicyStructure
from being used. Values 1 and 2 mean that this SUPAPolicyStructure
is administratively enabled or disabled, respectively. A value of
3 means that this SUPAPolicyStructure is in a special test mode
and SHOULD NOT be used as part of an OAM&P policy.
5.3.1.2. The Attribute "supaPolContinuumLevel"
This is an optional non-negative integer attribute. It defines
the level of abstraction, or policy continuum level [10], of this
particular SUPAPolicy. The value assignment of this class is
dependent on the application; however, it is recommended that
for consistency with other SUPA attributes, the value of 0 is
reserved for initialization and/or error conditions.
By convention, lower values represent more abstract levels of the
policy continuum. For example, a value of 1 could represent
business policy, a value of 2 could represent application-specific
policies, and a value of 3 could represent low=level policies for
network administrators.
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5.3.1.3. The Attribute "supaPolDeployStatus"
This is an optional enumerated, non-negative integer attribute. The
purpose of this attribute is to indicate that this SUPAPolicy can
or cannot be deployed by the policy management system. This
attribute enables the policy manager to know which SUPAPolicies to
retrieve, and may be useful for the policy execution system for
planning the staging of SUPAPolicies. Values include:
0: undefined
1: deployed and enabled
2: deployed and in test
3: deployed but not enabled
4: ready to be deployed
5: cannot be deployed
If the value of this attribute is 0 or 5, then the policy
management system SHOULD ignore this SUPAPolicy. Otherwise, the
policy management MAY use this SUPAPolicy.
5.3.1.4. The Attribute "supaPolExecStatus"
This is an optional attribute, which is an enumerated,
non-negative integer. It defines the current execution status
of this SUPAPolicy. Values include:
0: undefined
1: executed and SUCCEEDED (operational mode)
2: executed and FAILED (operational mode)
3: currently executing (operational mode)
4: ready to execute (operational mode)
5: executed and SUCCEEDED (test mode)
6: executed and FAILED (test mode)
7: currently executing (test mode)
8: ready to execute (test mode)
5.3.1.5. The Attribute "supaPolExecFailStrategy"
This is an optional non-negative, enumerated integer that defines
what actions, if any, should be taken by this
SUPAPolicyStructure object if it fails to execute correctly.
Note that some systems may not be able to support all options
specified in this enumeration. If rollback is supported by the
system, then option 2 may be skipped. Options 3 and 4 can be used
by systems that do and do not support rollback. Values include:
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0: undefined
1: attempt rollback of all actions taken and stop execution
2: attempt rollback of only the action that failed and stop
execution
3: stop execution but do not rollback any actions
4: ignore failure and continue execution
A value of 0 can be used as an error condition. A value of 1 means
that ALL execution is stopped, rollback of all actions (whether
successful or not) is attempted, and that SUPAPolicies that
otherwise would have been executed are ignored. A value of 2 means
that execution is stopped, and rollback is attempted for ONLY the
SUPAPolicy that failed to execute correctly.
5.3.2. SUPAPolicyStructure Relationships
The SUPAPolicyStructure class owns four relationships, which are
defined in the following subsections.
5.3.2.1. The Aggregation "SUPAHasPolicySource"
This is an optional aggregation, and defines the set of
SUPAPolicySource objects that are attached to this particular
SUPAPolicyStructure object. The semantics of this aggregation
are defined by the SUPAHasPolicySourceDetail association class.
PolicySource objects are used for authorization policies, as well
as to enforce deontic and alethic logic.
The multiplicity of this aggregation is 0..n - 0..n. This means
that it is an optional aggregation; zero or more SUPAPolicySource
objects may be aggregated by this SUPAPolicyStructure object,
and zero or more SUPAPolicyStructure objects may aggregate this
particular SUPAPolicySource object.
5.3.2.2. The Association Class "SUPAHasPolicySourceDetail"
This is an optional association class, and defines the semantics
of the SUPAHasPolicySource aggregation. The attributes and
relationships of this class can be used to define which
SUPAPolicySource objects can be attached to which particular set
of SUPAPolicyStructure objects.
5.3.2.2.1. The Attribute "supaPolSrcIsAuthenticated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicySource object has been
authenticated by this particular SUPAPolicyStructure object.
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5.3.2.2.2. The Attribute "supaPolSrcIsTrusted"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this particular SUPAPolicySource object
has been verified to be trusted by this particular
SUPAPolicyStructure object.
5.3.2.3. The Aggregation "SUPAHasPolicyTarget"
This is an optional aggregation, and defines the set of
SUPAPolicyTargets that are attached to this particular
SUPAPolicyStructure. The semantics of this aggregation is
defined by the SUPAHasPolicyTargetDetail association class. The
purpose of this class is to explicitly identify managed objects
that will be affected by the execution of one or more SUPAPolicies.
The multiplicity of this aggregation is 0..n - 0..n. This means
that it is an optional aggregation; zero or more SUPAPolicyTarget
objects may be aggregated by this SUPAPolicyStructure object,
and zero or more SUPAPolicyStructure objects may aggregate this
particular SUPAPolicyTarget object.
5.3.2.4. The Association Class "SUPAHasPolicyTargetDetail"
This is an optional association class, and defines the semantics
of the SUPAPolicyTargetOf aggregation. The attributes and
relationships of this class can be used to define which
SUPAPolicyTargets can be attached to which particular set of
SUPAPolicyStructure objects.
5.3.2.4.1. The Attribute "supaPolTgtIsAuthenticated"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAPolicyTarget object has been
authenticated by this particular SUPAPolicyStructure object.
5.3.2.4.2. The Attribute "supaPolTgtIsEnabled"
This is an optional Boolean attribute. If its value is TRUE, then
this SUPAPolicyTarget is able to be used as a SUPAPolicyTarget.
This means that it meets two specific criteria:
1. it has agreed to play the role of a SUPAPolicyTarget (i.e.,
it is willing to have SUPAPolicies applied to it, and
2. it is able to either process (directly or with the aid of
a proxy) SUPAPolicies or receive the results of a processed
SUPAPolicy and apply those results to itself.
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5.3.2.5. The Association "SUPAHasPolExecFailTakeAction"
This is an optional association that defines which, if any, actions
should be taken if this SUPAPolicyStructure object instance fails
to execute correctly. The semantics of this association are defined
in the SUPAHasPolExecFailTakeActionDetail association class.
For a given SUPAPolicyStructure object A, this association defines
a set of policy action objects B to execute if (and only if) the
SUPAPolicyStructure object A failed to execute correctly. The
multiplicity of this association is defined as 0..n on the owner
(A) side and 1..n on the part (B) side. This means that this
association is optional; if it is instantiated, then at least one
SUPAPolicyStructure MUST be instantiated by this
SUPAPolicyStructure object. Similarly, one or more
SUPAPolicyStructure objects may be associated with this given
SUPAPolicyStructure object.
5.3.2.6. The Association Class "SUPAHasPolExecFailTakeActionDetail"
This is an optional concrete class that defines the semantics for
the SUPAHasPolExecFailTakeAction association. The attributes and/or
relationships of this association class can be used to determine
which policy action objects are executed in response to a failure
of the SUPAPolicyStructure object instance that owns this
association. The association relates the policy actions from one
SUPAPolicyStructure B to be executed if a SUPAPolicyStructure A
fails to execute properly. Figure 18 illustrates this approach.
A
+---------------------------+ 0..n
| +---------------------------------+
| | SUPAHasPolExecFailTakeAction |
| SUPAPolicyStructure |/ |
| + --------------+-----------------+
| |\ ^
+---------------------------+ 1..n |
|
C |
+------------------+-----------------+
| SUPAHasPolExecFailTakeActionDetail |
+------------------------------------+
Figure 18. SUPAHasPolExecFailTakeAction Association
5.3.2.6.1. The Attribute "supaPolExecFailTakeActionEncoding"
This is an optional enumerated, non-negative integer attribute
that defines how to find the set of SUPAPolicyActions contained
in each element of the supaPolExecFailTakeActionName class
attribute. Values include:
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0: undefined
1: String
2: GUID
3: UUID
4: URI
5: FQDN
5.3.2.6.2. The Attribute "supaPolExecFailTakeActionName[1..n]"
This is an optional array of string attributes that identifies the
set of policy actions to take if the SUPAPolicyStructure object
that owns this association failed to execute properly. The
interpretation of this string attribute is defined by the
supaPolExecFailTakeActionEncoding class attribute. The association
defines the SUPAPolicyStructure that contains the set of policy
actions to execute, and this attribute defines which of these
actions are to be executed. Note that there is no need to execute
a SUPAPolicy, since the event and failure have already occurred.
Note: [1..n] means that this is a multi-valued property that has
at least one (and possibly more) attributes.
5.3.2.7. The Aggregation "SUPAHasPolicyClause"
This is an optional aggregation that defines the set of
SUPAPolicyClauses that are aggregated by this particular
SUPAPolicyStructure instance. The semantics of this
aggregation are defined by the SUPAHasPolicyClauseDetail
association class.
Every SUPAPolicyStructure object instance MUST aggregate at
least one SUPAPolicyClause object instance. However, the
converse is NOT true. For example, a SUPAPolicyClause could be
instantiated and then stored for later use in a policy repository.
Furthermore, the same SUPAPolicyClause could be used by zero or
more SUPAPolicyStructure object instances at a given time. Thus,
the multiplicity of this aggregation is defined as 0..1 on the
aggregate (i.e., the SUPAPolicyStructure side) and 1..n on the
part (i.e., the SUPAPolicyClause side). This means that at
least one SUPAPolicyClause MUST be aggregated by this
SUPAPolicyStructure object. Similarly, a SUPAPolicyClause may
be aggregated by this particular SUPAPolicyStructure object.
5.3.2.8. The Association Class "SUPAHasPolicyClauseDetail"
This is an optional association class, and defines the semantics
of the SUPAHasPolicyClause aggregation. The attributes and/or
relationships of this association class can be used to determine
which SUPAPolicyClauses are aggregated by which
SUPAPolicyStructure objects.
Attributes will be added to this class at a later time.
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5.4. The Abstract Class "SUPAPolicyComponentStructure"
This is a mandatory abstract class that is the superclass of all
objects that represent different types of components of a
SUPAPolicy. Different types of policies have different types of
structural components. However, all of these are used in at least
one type of policy. This class represents a convenient control
point for defining characteristics and behavior that are common
to objects that serve as components of a policy.
Note that there are significant differences between the definition
of this class, and its attributes, and the definition of the
corresponding class (and its attributes) in [5].
5.4.1. SUPAPolicyComponentStructure Attributes
No attributes are currently defined for the
SUPAPolicyComponentStructure class.
5.4.2. SUPAPolicyComponentStructure Relationships
SUPAPolicyComponentStructure participates in a single relationship,
SUPAHasDecoratedPolicyComponent, as defined in section 5.7.3.
5.5. The Abstract Class "SUPAPolicyClause"
This is a mandatory abstract class that separates the
representation of a SUPAPolicy from its implementation.
SUPAPolicyClause was abstracted from DEN-ng [2]. This abstraction
is missing in [RFC3060], [RFC3460], [4], and [6]. This class is
called PolicyStatement in [5], but the class and relationship
definitions differ significantly from the corresponding designs
in this document.
A SUPAPolicyClause contains an individual or group of related
functions that are used to define the content of a policy. More
specifically, since the number and type of functions that make up
a SUPAPolicyClause can vary, the decorator pattern is used, so
that the contents of a SUPAPolicyClause can be adjusted
dynamically at runtime without affecting other objects.
This document defines two different types of policy clauses:
SUPAEncodedClause (which is generic, and can be used by any
type of policy), and SUPABooleanClause (which is also generic,
but is typically used by SUPAECAPolicyRule objects).
SUPAPolicyClauses are objects in their own right, which
facilitates their reuse. SUPAPolicyClauses can aggregate a set
of any of the subclasses of SUPAPolicyComponentDecorator, which
was shown in Figure 10. These four subclasses provide four
different ways to construct a SUPAPolicyClause:
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1) SUPAPolicyTerm, which enables constructing a {variable,
operator, value} expression for building DUPAPolicyClauses
2) SUPAEncodedClause, which enables policy clauses to be
formed as an encoded object (e.g., to pass YANG or CLI code)
3) SUPAPolicyCollection, which defines a collection of objects
that requires further processing by the policy management
system in order to be made into a SUPAPolicyClause
4) SUPAECAComponent, which enables policy clauses to be formed
using (reusable) Event, Condition, and/or Action objects
SUPAPolicyClauses are aggregated by a SUPAPolicyStructure
object, which enables all types of SUPAPolicies to uniformly be
made up of one or more SUPAPolicyClauses.
5.5.1. SUPAPolicyClause Attributes
This section defines the attributes of the SUPAPolicyClause
class, which are inherited by all SUPAPolicyClause subclasses.
5.5.1.1. The Attribute "supaPolClauseExecStatus"
This is an optional enumerated non-negative integer attribute. It
defines whether this SUPAPolicyClause is currently in use and, if
so, what its execution status is. This attribute can also be used
to place this particular SUPAPolicyClause into a specific execution
state, such as enabled (values 1-4), in test (value 5) or disabled
(value 6). Values include:
0: Unknown (an error state)
1: Completed (i.e., successfully executed, but now idle)
2: Working (i.e., in use and no errors reported)
3: Not Working (i.e., in use, but errors have been reported)
4: Available (i.e., could be used, but currently isn't)
5: In Test (i.e., cannot be used as part of an OAM&P policy)
6: Disabled (i.e., not available for use)
Value 0 denotes an error that prevents this SUPAPolicyClause
from being used. Value 1 means that this SUPAPolicyClause has
successfully finished execution, and is now idle. Value 2 means
that this SUPAPolicyClause is in use; in addition, this
SUPAPolicyClause is working correctly. Value 3 is the same as
value 2, except that this SUPAPolicyClause is not working
correctly. Value 4 means that this SUPAPolicyClause is available,
but not currently in use. Value 5 means that this SUPAPolicyClause
is in a special test state. A test state signifies that it SHOULD
NOT be used to evaluate OAM&P policies. A value of 6 means that
this SUPAPolicyClause is unavailable for use.
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5.5.2. SUPAPolicyClause Relationships
SUPAPolicyClause participates in a single relationship,
SUPAHasPolicyClause, as defined in section 5.3.2.7. Note that
SUPAPolicyClause uses the decorator pattern to "wrap" this object
with instances of the (concrete) subclasses of the
SUPAPolicyComponentDecorator object.
5.6. The Concrete Class "SUPAEncodedClause"
This is a mandatory concrete class that refines the behavior of a
SUPAPolicyClause.
This class defines a generalized extension mechanism for
representing SUPAPolicyClauses that have not been modeled
with other SUPAPolicy objects. Rather, the contents of the policy
clause are directly encoded into the attributes of the
SUPAEncodedClause. Hence, SUPAEncodedClause objects are reusable
at the object level, whereas SUPABooleanClause clauses are reusable
at the individual Boolean expression level.
This class uses two of its attributes (supaEncodedClauseContent and
supaEncodedClauseEncoding) for defining the content and type of
encoding used in a given SUPAPolicyClause. The benefit of a
SUPAEncodedClause is that it enables direct encoding of the text of
the SUPAPolicyClause, without having the "overhead" of using other
objects. However, note that while this method is efficient, it
does not reuse other SUPAPolicy objects.
5.6.1. SUPAEncodedClause Attributes
This section defines the attributes of the SUPAEncodedClause class.
5.6.1.1. The Attribute "supaEncodedClauseContent"
This is a mandatory string attribute, and defines the content of
this clause. It works with another class attribute, called
supaEncodedClauseEncoding, which defines how to interpret the
value of this attribute (e.g., as a string or reference). These
two attributes form a tuple, and together enable a machine to
understand the syntax and value of this object instance.
5.6.1.2. The Attribute "supaEncodedClauseEncoding"
This is a mandatory integer attribute, and defines how to
interpret the value of this encoded clause. It works with another
class attribute, called supaEncodedClauseContent, which defines
the content of the encoded clause. These two attributes form a
tuple, and together enable a machine to understand the syntax and
value of the encoded clause for the object instance of this class.
Values include:
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0: undefined
1: String
2: GUID
3: UUID
4: URI
5: FQDN
5.6.1.3. The Attribute "supaEncodedClauseResponse"
This is an optional Boolean attribute that emulates a Boolean
response of this clause, so that it may be combined with other
subclasses of the SUPAPolicyClause that provide a status as to
their correctness and/or evaluation state. This enables this
object to be used to construct more complex Boolean clauses.
5.6.2. SUPAEncodedClause Relationships
SUPAPolicyClause participates in a single inherited relationship,
SUPAHasPolicyClause, as defined in section 5.3.2.7.
5.7. The Abstract Class "SUPAPolicyComponentDecorator"
This is a mandatory class, and is used to implement the decorator
pattern. The decorator pattern enables all or part of one or more
objects to "wrap" another concrete object. This means that any
any concrete subclass of SUPAPolicyClause is wrapped by any
concrete subclass of SUPAPolicyComponentDecorator, as shown in
Figure 19 below.
A
+------------------------------+
| | 1..n
| SUPAPolicyComponentStructure +--------+
| | | used to wrap
+------------------------------+ | concrete
/ \ | subclasses of
I | PolicyClause
I |
+---------------+--------------+ / \
I I A
A I A I \ / 0..1
+----------+---------+ +--------------+-----+---------+
| SUPAPolicyClause | | SUPAPolicyComponentDecorator |
+----------+---------+ +--------------+---------------+
I I
I I
/ \ / \
Concrete Subclasses, Concrete Subclasses
(e.g., SUPAEncodedClause) (e.g., SUPAPolicyCollection)
(object being wrapped) (wrapping object(s))
Figure 19. The PolicyComponent Decorator Pattern
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5.7.1. The Decorator Pattern
Each SUPAPolicyComponentDecorator object HAS_A (i.e., wraps) a
concrete instance of the SUPAPolicyClause object. This means that
the SUPAPolicyComponentDecorator object has an instance variable
that holds a reference to a SUPAPolicyClause object. Since the
SUPAPolicyComponentDecorator object has the same interface as the
SUPAPolicyClause object, the SUPAPolicyComponentDecorator object
(and all of its subclasses) are transparent to clients of the
SUPAPolicyClause object (and its subclasses). This means that
SUPAPolicyComponentDecorator object instances can add attributes
and/or methods to those of the concrete instance of the chosen
subclass of SUPAPolicyClause.
Figure 19 shows how this is done for methods. 19a shows the
initial object to be wrapped; 19b shows SUPAPolicyCollection
wrapping SUPAEncodedClause; 19c shows SUPAGenericDecoratedComponent
wrapping SUPAPolicyCollection.
+-------------------+
| SUPAEncodedClause |
| eval() |
+-------------------+
(a) Initial Object
===>
+------------------------+
| SUPAPolicyCollection |
| eval() |
| +-------------------+ |
| | SUPAEncodedClause | |
| | eval() | |
| +-------------------+ |
+------------------------+
(b) SUPAPolicyCollection "wraps" SUPAEncodedClause
===>
+--------------------------------+
| SUPAGenericDecoratedComponent |
| eval() |
| +-----------------------+ |
| | SUPAPolicyCollection | |
| | eval() | |
| | +-------------------+ | |
| | | SUPAEncodedClause | | |
| | | eval() | | |
| | +-------------------+ | |
| +-----------------------+ |
+--------------------------------+
(c) SUPAGenericDecoratedComponent "wraps" SUPAPolicyCollection
Figure 20. Conceptual Depiction of eval() Decorated Method
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When eval() is called in the outermost object
(SUPAGenericDecoratedComponent), it delegates to the eval() method
of SUPAPolicyCollection, which in turn delegates to the eval()
method of SUPAEncodedClause. This method executes and returns the
results to SUPAPolicyCollection, which executes and returns the
results to SUPAGenericDecoratedComponent, which executes and returns
the final result.
5.7.2. SUPAPolicyComponentDecorator Attributes
Currently, there are two attributes defined for this class, which
are described in the following subsections. Both attributes are
used by subclasses to constrain the behavior of that subclass;
they do **not** affect the relationship between the concrete
subclass of SUPAPolicyComponentDecorator that is wrapping the
concrete subclass of SUPAPolicyClause. This is different
than the use of similar attributes defined in the
SUPAHasDecoratedPolicyComponentDetail association class (which
are used to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of the
SUPAHasDecoratedPolicyComponent object that is wrapping it).
Note that [2] does not define any attributes for this class.
5.7.2.1. The Attribute "supaPolCompConstraintEncoding"
This is a mandatory non-negative enumerated integer that defines
how to interpret each string in the supaPolCompConstraint class
attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
Enumerations 1-3 are dedicated to OCL (with OCL 2.4 being the
latest version as of this writing). QVT defines a set of languages
(the two most powerful and useful are defined by enumerations 4
and 5). Alloy is a language for describing constraints, and uses a
SAT solver to guarantee correctness.
5.7.2.2. The Attribute "supaAPolCompConstraint[0..n]"
This is a mandatory array of string attributes. Each attribute
specifies a constraint to be applied using the encoding defined in
the supaPolCompConstraintEncoding class attribute. This provides
a more rigorous and flexible treatment of constraints than is
possible in [RFC3460].
Note: [0..n] means that this is a multi-valued property that may
have zero or more attributes.
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5.7.3. SUPAPolicyComponentDecorator Relationships
One relationship is currently defined for this class, which is
described in the following subsection.
5.7.3.1. The Aggregation "SUPAHasDecoratedPolicyComponent"
This is a mandatory aggregation, and is part of a decorator
pattern. It is used to enable a concrete instance of a
SUPAPolicyComponentDecorator to dynamically add behavior to a
specific type of SUPAPolicyClause object. The semantics of this
aggregation are defined by the
SUPAHasDecoratedPolicyComponentDetail association class.
5.7.3.2. The Association Class
"SUPAHasDecoratedPolicyComponentDetail"
This is a mandatory concrete association class, and defines the
semantics of the SUPAHasDecoratedPolicyComponent aggregation. The
purpose of this class is to use the Decorator pattern to determine
which SUPAPolicyComponentDecorator object instances, if any, are
required to augment the functionality of the concrete subclass of
SUPAPolicyClause that is being used.
Currently, there are two attributes defined for this class, which
are described in the following subsections. Both attributes are
used in this association class to constrain the **relationship**
between the concrete subclass of SUPAPolicyComponentDecorator that
is wrapping the concrete subclass of SUPAPolicyClause. Note that
class attributes of SUPAPolicyComponentDecorator (see section
5.9.2) only affect that specific subclass.
5.7.3.2.1. The Attribute "supaDecoratedConstraintEncoding"
This is a mandatory non-negative enumerated integer that defines
how to interpret each string in the supaDecoratedConstraint class
attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
Enumerations 1-3 are dedicated to OCL (with OCL 2.4 being the
latest version as of this writing). QVT defines a set of languages
(the two most powerful and useful are defined by enumerations 4
and 5). Alloy is a language for describing constraints, and uses a
SAT solver to guarantee correctness.
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5.7.3.2.2. The Attribute "supaDecoratedConstraint[0..n]"
This is a mandatory array of string attributes. Its purpose is to
collect a set of constraints to be applied to a decorated object.
The interpretation of each constraint in the array is defined in
the supaDecoratedConstraintsEncoding class attribute.
Note: [0..n] means that this is a multi-valued property that may
have zero or more attributes.
5.7.4. Illustration of Constraints in the Decorator Pattern
The following example will illustrate how the different constraints
defined in sections 5.7.2 (class attribute constraints) and section
5.7.3 (relationship constraints) can be used.
Figure 21 builds a simple SUPAPolicyClause that has both types
of relationships.
A A
+------------------+ 0..1 +----------------------------+
| | 1..n / \| |
| SUPAPolicyClause +------+----- A +SUPAPolicyComponentDecorator|
| | ^ \ /| |
+---------+--------+ | +-----------+----------------+
I | I
I | I
C I | C I
+--------+--------+ | +---------+----------+
|SUPAEncodedClause| | |SUPAPolicyCollection|
+-----------------+ | +--------------------+
|
C |
+-----------------+-------------------+
|SUPAHasDecoratedPolicyComponentDetail|
+-------------------------------------+
Figure 21. Constraints in the Decorator Pattern
Figure 21 says that a SUPAPolicyClause, realized as a
SUPAEncodedClause, is wrapped by a SUPAPolicyCollection object.
The attributes in the SUPAPolicyComponentDecorator object are used
to constrain the attributes in the SUPAPolicyCollection object,
while the attributes in the SUPAHasDecoratedPolicyComponentDetail
object are used to contrain the behavior of the aggregation
(SUPAHasDecoratedPolicyComponent). For example, the attributes in
the SUPAPolicyComponentDecorator object could restrict the data
type and range of the components in the SUPAPolicyCollection, while
the attributes in the SUPAHasDecoratedPolicyComponentDetail object
could restrict which SUPAPolicyCollection objects are allowed to be
used with which SUPAEncodedClauses.
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5.8. The Abstract Class "SUPAPolicyTerm"
This is a mandatory abstract class that is the parent of
SUPAPolicy objects that can be used to define a standard way to
test or set the value of a variable. It does this by defining a
3-tuple, in the form {variable, operator, value}, where each
element of the 3-tuple is defined by a concrete subclass of the
appropriate type (i.e., SUPAPolicyVariable, SUPAPolicyOperator,
and SUPAPolicyValue classes, respectively). For example, a
generic test or set of the value of a variable is expressed as:
{variable, operator, value}.
For event and condition clauses, this is typically as written above
(e.g., does variable = value); for action clauses, it is typically
written as <operator> <variable> <value> (e.g., SET var to 1). A
class diagram is shown in Figure 22.
A
+----------------+
| SUPAPolicyTerm |
+--------+-------+
/ \
I
I
I
+-----------------+---+--------------------+
I I I
I I I
C I C I C I
+--------+---------+ +--------+---------+ +-------+-------+
|SUPAPolicyVariable| |SUPAPolicyOperator| |SUPAPolicyValue|
+------------------+ +------------------+ +---------------+
Figure 22. SUPAPolicyTerm Class Hierarchy
Note that generic test and set expressions do not have to only use
objects that are subclasses of SUPAPolicyTerm. For example, the
polVendorDecoratedContent attribute of the
SUPAGenericDecoratedComponent could be used as the variable (or the
value) term of a get or set expression.
Hence, the utility of the subclasses of SUPAPolicyTerm is in the
ability of its subclasses to define a generic framework for
implementing get and set expressions. This is in contrast to
previous designs (e.g., [RFC3460] and [6]), which depended on
defining a broad set of subclasses of PolicyVariable and
PolicyValue. (Note that [4] does not have this generic capability).
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5.8.1. SUPAPolicyTerm Attributes
Currently, SUPAPolicyTerm defines a single attribute, as described
in the following subsection. Constraints on the subclasses of
SUPAPolicyTerm can be applied in two different ways:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyTerm class
5.8.1.1. The Attribute "supaPolTermIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is true, then this particular SUPAPolicyTerm subclass
(which represents a term) is negated; otherwise, it is not.
5.8.2. SUPAPolicyTerm Relationships
Currently, no dedicated relationships are defined for the
SUPAPolicyTerm class (as there are in [RFC3460] and [6]) that
aggregate policy variable and policy value objects into a policy
rule). This is:
1) to enable the subclasses of SUPAPolicyTerm to be used by
other SUPAPolicyComponentDecorator objects, and
2) because the decorator pattern replaces how such relationships
were used in [RFC3460] and [6].
SUPAPolicyTerm, and its subclasses, inherit the
SUPAHasDecoratedPolicyComponent aggregation, which was defined in
section 5.7.3.
5.9. The Concrete Class "SUPAPolicyVariable"
This is a mandatory concrete class that defines information that
forms a part of a SUPAPolicyClause. It specifies a concept or
attribute that represents a variable, which should be compared to
a value, as specifed in this SUPAPolicyClause. If it is used in
a SUPAECAPolicyRule, then its value MAY be able to be changed at
any time, including run-time, via use of the decorator pattern.
Note that this is not possible in previous designs ([RFC3460, [4],
and [6]).
The value of a SUPAPolicyVariable is typically compared to the
value of a SUPAPolicyValue using the type of operator defined in
a SUPAPolicyOperator. However, other objects may be used instead
of a SUPAPolicyValue object, and other operators may be defined
in addition to those defined in the SUPAPolicyOperator class.
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SUPAPolicyVariables are used to abstract the representation of a
SUPAPolicyRule from its implementation. Some SUPAPolicyVariables
are restricted in the values and/or the data type that they may
be assigned. For example, port numbers cannot be negative, and
they cannot be floating-point numbers. These and other constraints
may be defined in two different ways:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyVariable class
Please refer to the examples in section 7, which show how to
restrict the value, data type, range, and other semantics of the
SUPAPolicyVariable when used in a SUPAPolicyClause.
5.9.1. Problems with the RFC3460 Version of PolicyValue
Please see Appendix A for a detailed comparison.
5.9.2. SUPAPolicyVariable Attributes
SUPAPolicyVariable defines one attribute, as described below.
5.9.2.1. The Attribute "supaPolVarName"
This is an optional string attribute that contains the name of
this SUPAPolicyVariable. This variable name forms part of the
{variable, operator, value} canonical form of a SUPAPolicyClause.
5.9.3. SUPAPolicyVariable Relationships
Currently, no relationships are defiend for the SUPAPolicyVariable
class (note that the decorator pattern obviates the need for
relationships such as those in [RFC3460] and [6]).
SUPAPolicyVariable, and its subclasses, inherit the
SUPAHasDecoratedPolicyComponent aggregation, which was defined in
section 5.7.3.
5.10. The Concrete Class "SUPAPolicyOperator"
This is a mandatory concrete class for modeling different types of
operators that are used in a SUPAPolicyClause.
The restriction of the type of operator used in a SUPAPolicyClause
restricts the semantics that can be expressed in that
SUPAPolicyClause. It is typically used with SUPAPolicyVariables
and SUPAPolicyValue to form a SUPAPolicyClause.
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5.10.1. Problems with the RFC3460 Version
Please see Appendix A for a detailed comparison.
5.10.2. SUPAPolicyOperator Attributes
Currently, SUPAPolicyOperator defines a single generic attribute,
as described below.
5.10.2.1. The Attribute "supaPolOpType"
This is a mandatory non-negative enumerated integer that specifies
the various types of operators that are allowed to be used in this
particular SUPAPolicyClause. Values include:
0: Unknown
1: Greater than
2: Greater than or equal to
3: Less than
4: Less than or equal to
5: Equal to
6: Not equal to
7: IN
8: NOT IN
9: SET
10: CLEAR
11: BETWEEN
Note that 0 is an unacceptable value. Its purpose is to support
dynamically building a SUPAPolicyClause by enabling the
application to set the value of this attribute to a standard
default value if the real value is not yet known.
Additional operators may be defined in future work. For example,
if SUPAPolicyVariables and SUPAPolicyValues are expanded to/from
include structured objects, then "deep" versions of operators
1-6 could also be defined. In this case, values 1-6 will be
edited to explicitly indicate that they perform "shallow"
comparison operations.
5.10.3. SUPAPolicyOperator Relationships
Currently, no relationships are defiend for the SUPAPolicyOperator
class (note that the decorator pattern obviates the need for
relationships such as those in [6]). SUPAPolicyOperator, and its
subclasses, inherit the SUPAHasDecoratedPolicyComponent
aggregation, which was defined in section 5.7.3.
Please refer to the examples in section 7, which show how to
restrict the value, data type, range, and other semantics of the
SUPAPolicyOperator when used in a SUPAPolicyClause.
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5.11. The Concrete Class "SUPAPolicyValue"
The SUPAPolicyValue class is a mandatory concrete class for
modeling different types of values and constants that occur in a
SUPAPolicyClause.
SUPAPolicyValues are used to abstract the representation of a
SUPAPolicyRule from its implementation. Therefore, the design of
SUPAPolicyValues depends on two important factors. First, just as
with SUPAPolicyVariables (see Section 5.11), some types of
SUPAPolicyValues are restricted in the values and/or the data
type that they may be assigned. Second, there is a high likelihood
that specific applications will need to use their own variables
that have specific meaning to a particular application.
In general, there are two ways to apply constraints to an object
instance of a SUPAPolicyValue:
1. use SUPAPolicyComponentDecorator attributes to constrain
just that individual subclass, and/or
2. use SUPAHasDecoratedPolicyComponentDetail association class
attributes to constrain the relationship between the concrete
subclass of SUPAPolicyClause and the concrete subclass of
the SUPAPolicyValue class
The value of a SUPAPolicyValue is typically compared to the value
of a SUPAPolicyVariable using the type of operator defined in
a SUPAPolicyOperator. However, other objects may be used instead
of a SUPAPolicyVariable object, and other operators may be defined
in addition to those defined in the SUPAPolicyOperator class.
5.11.1. Problems with the RFC3460 Version of PolicyValue
Please see Appendix A for a detailed comparison.
5.11.2. SUPAPolicyValue Attributes
Currently, SUPAPolicyValue defines two generic attributes, as
described below.
5.11.2.1. The Attribute "supaPolValContent[0..n]"
This is a mandatory attribute that defines an array of strings.
The array contains the value(s) of this SUPAPolicyValue object
instance. Its data type is defined by the supaPolValEncoding
class attribute.
Note: [0..n] means that this is a multi-valued property that has
zero or more attributes.
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5.11.2.2. The Attribute "supaPolValEncoding"
This is a mandatory string attribute that contains the data type
of the SUPAPolicyValue object instance. Its value is defined by
the supaPolValContent class attribute. Values include:
0: Undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
10: NULL
A string is a sequence of zero or more characters. An Integer is
a whole number (e.g., it has no fractional part). A Boolean
represents the values TRUE and FALSE. A floating point number may
contain fractional values, as well as an exponent. A DateTime
represents a value that has a date and/or a time component (as in
the Java or Python libraries). A NULL explicitly models the lack
of a value.
5.11.3. SUPAPolicyValue Relationships
Currently, no relationships are defiend for the SUPAPolicyValue
class (note that the decorator pattern obviates the need for
relationships such as those in [6]). SUPAPolicyValue, and its
subclasses, inherit the SUPAHasDecoratedPolicyComponent
aggregation, which was defined in section 5.7.3.
Please refer to the examples in section 7, which show how to
restrict the value, data type, range, and other semantics of the
SUPAPolicyValue when used in a SUPAPolicyClause.
5.12. The Concrete Class "SUPAGenericDecoratedComponent"
A SUPAGenericDecoratedComponent enables a custom, vendor-specific
object to be defined and used in a SUPAPolicyClause. This class
was derived from [2], but is not present in [RFC3460], [4], [5],
or [6].
This should not be confused with the SUPAEncodedClause class. The
SUPAGenericDecoratedComponent class represents a single, atomic,
vendor-specific object that defines a **portion** of a
SUPAPolicyClause, whereas a SUPAEncodedClause, which may or
may not be vendor-specific, represents an **entire**
SUPAPolicyClause.
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5.12.1. SUPAGenericDecoratedComponent Attributes
Currently, SUPAGenericDecoratedComponent defines two generic
attributes, as described below.
5.12.1.1. The Attribute "supaVendorDecoratedCompContent[0..n]"
This is a mandatory attribute that defines an array of strings.
This array contains the value(s) of the
SUPAGenericDecoratedComponent object instance. Its data type is
defined by the supaVendorDecoratedEncoding class attribute.
Note: [0..n] means that this is a multi-valued property that has
zero or more attributes.
5.12.1.2. The Attribute "supaVendorDecoratedCompEncoding"
This is a mandatory integer attribute that defines the format of
the supaVendorDecoratedContent class attribute. Values include:
0: undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6: GUID
7: UUID
8: URI
9: FQDN
10: NULL
A string is a sequence of zero or more characters. An Integer is
a whole number (e.g., it has no fractional part). A Boolean
represents the values TRUE and FALSE. A floating point number may
contain fractional values, as well as an exponent. A DateTime
represents a value that has a date and/or a time component (as in
the Java or Python libraries). A NULL explicitly models the lack
of a value.
5.12.2. SUPAGenericDecoratedComponent Relationships
Currently, no relationships are defiend for the
SUPAGenericDecoratedComponent class (note that the decorator
pattern obviates the need for relationships such as those in [6]).
SUPAGenericDecoratedComponent participates in a single relationship,
SUPAHasDecoratedPolicyComponent, as defined in section 5.7.3.
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5.13. The Concrete Class "SUPAPolicyCollection"
A SUPAPolicyCollection is an optional concrete class that enables
a collection (e.g., set, bag, or other, more complex, collections
of elements) of **arbitrary objects** to be defined and used as
part of a SUPAPolicyClause. This class was derived from [2], but
is not present in [RFC3460], [4], [5], or [6].
5.13.1. Motivation
One of the problems with ECA policy rules is when a set of events
or conditions needs to be tested. For example, if a set of events
is received, the policy system may need to wait for patterns of
events to emerge (e.g., any number of Events of type A, followed
by either one event of type B or two events of type Event C).
Similarly, a set of conditions, testing the value of an attribute,
may need to be performed. Both of these represent behavior
similar to a set of if-then-else statements or a switch statement.
It is typically not desirable for the policy system to represent
each choice in such conditions as its own policy clause (i.e., a
3-tuple), as this creates object explosion and poor performance.
Furthermore, in these cases, it is often required to have a set of
complex logic to be executed, where the logic varies according to
the particular event or condition that was selected. It is much
too complex to represent this using separate objects, especially
when the logic is application- and/or vendor-specific.
However, recall that one of the goals of this document was to
facilitate the machine-driven construction of policies. Therefore,
a solution to this problem is needed.
5.13.2. Solution
Therefore, this document defines the concept of a collection of
entities, called a SUPAPolicyCollection. Conceptually, the items
to be collected (e.g., events or conditions) are aggregated in
one or more SUPAPolicyCollection objects of the appropriate type.
Another optional SUPAPolicyCollection object could be used to
aggregate logic blocks (including SUPAPolicies) to execute.
Once finished, all appropriate SUPAPolicyCollection objects are
sent to an external system for evaluation.
The computation(s) represented by the SUPAPolicyCollection may be
part of a larger SUPAPolicyClause, since SUPAPolicyCollection is a
subclass of SUPAPolicyComponentDecorator, and can be used to
decorate a SUPAPolicyClause. Therefore, the external system is
responsible for providing a Boolean TRUE or FALSE return value, so
that the policy system can use that value to represent the
computation of the function(s) performed in the
SUPAPolicyCollection in a Boolean clause.
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5.13.3. SUPAPolicyCollection Attributes
Currently, SUPAGenericDecoratedComponent defines five attributes,
as described below.
5.13.3.1. The Attribute "supaPolCollectionContent[0..n]"
This is an optional attribute that defines an array of strings.
Each string in the array identifies a domain-suitable identifier of
an object that is collected by this SUPAPolicyCollection instance.
Note: [0..n] means that this is a multi-valued property that has
zero or more attributes.
5.13.3.2. The Attribute "supaPolCollectionEncoding"
This is an optional non-negative enumerated integer that defines
the data type of the content of this collection instance. Values
include:
0: undefined
1: by regex (regular expression)
2: by URI
For example, if the value of this attribute is 1, then each of
the strings in the supaPolCollectionContent attribute represent
a regex that contains all or part of a string to match the class
name of the object that is to be collected by this instance of
a SUPAPolicyCollection class.
5.13.3.3. The Attribute "supaPolCollectionFunction"
This is an optional non-negative enumerated integer that defines
the function of this collection instance. Values include:
0: undefined
1: event collection
2: condition collection
3: action collection
4: logic collection
Values 1-3 define a collection of objects that are to be used to
populate the event, condition, or action clauses, respectively, of
a SUPAECAPolicyRule. A value of 4 indicates that this collection
contains objects that define logic for processing a SUPAPolicy.
5.13.3.4. The Attribute "supaPolCollectionIsOrdered"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then all elements in this instance of this
SUPAPolicyCollection are ordered.
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5.13.3.5. The Attribute "supaPolCollectionType"
This is an optional non-negative enumerated integer that defines
the type of collection that this instance is. Values include:
0: undefined
1: set
2: bag (e.g., multi-set)
3: dictionary (e.g., associative array)
A set is an unordered collection of elements that MUST NOT have
duplicates. A bag is an unordered collection of elements; it MAY
also have duplicates. A dictonary is a table that associates a
key with a value.
Sets have a number of important functions, including:
o membership: returns TRUE if the element being tested is
in the set, and FALSE otherwise
o subset: returns TRUE if all elements in the first set
are also in the second set
o union: returns all elements from both sets with no
duplicates
o intersection: returns all elements that are in both sets
with no duplicates
o difference: returns all elements in the first set that
are not in the second set
Bags have a number of important functions in addition to the
functions defined for sets (note that while the above set of
functions for a set and a bag are the same, a bag is a different
data type than a set):
o multiplicity: returns the number of occurrences of an
element in the bag
o count: returns the number of all items, including
duplicates
o countDistinct: returns the number of items, where all
duplicates are ignored
A dictionary is an unordered set of key:value pairs, where each
key is unique within a given dictionary. The combination of a
key and a value is called an item. The format of an item is
defined as one element (the key) followed by a colon followed
by a second element (the value). Each item in a set of items is
separated by a comma. Keys MUST NOT be NULL; values MAY be NULL.
An example of a dictionary is {20:"FTP", 21:"FTP", 22: "SSH"}.
An example of a null dictionary is simply {}.
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5.13.4. SUPAPolicyCollection Relationships
Currently, no relationships are defiend for the
SUPAGenericDecoratedComponent class (note that the decorator
pattern obviates the need for relationships such as those in [6]).
SUPAPolicyCollection participates in a single relationship,
SUPAHasDecoratedPolicyComponent, as defined in section 5.7.3.
5.14. The Concrete Class "SUPAPolicySource"
This is an optional class that defines a set of managed entities
that authored, or are otherwise responsible for, this
SUPAPolicyRule. Note that a SUPAPolicySource does NOT
evaluate or execute SUPAPolicies. Its primary use is for
auditability and the implementation of deontic and/or alethic logic.
A class diagram is shown in Figure 12.
A SUPAPolicySource SHOULD be mapped to a role or set of roles
(e.g., using the role-object pattern [11]). This enables
role-based access control to be used to restrict which entities
can author a given policy. Note that Role is a type of
SUPAPolicyMetadata.
5.14.1. SUPAPolicySource Attributes
Currently, no attributes are defined for this class.
5.14.2. SUPAPolicySource Relationships
SUPAPolicySource participates in a single relationship,
SUPAHasPolicySource, as defined in section 5.3.2.1.
SUPAPolicySource, and its subclasses, inherit the
SUPAHasDecoratedPolicyComponent aggregation, which was
defined in section 5.7.3.
5.15. The Concrete Class "SUPAPolicyTarget"
This is an optional class that defines a set of managed entities
that a SUPAPolicy is applied to. Figure 12 shows a class diagram
of the SUPAPolicyTarget.
A managed object must satisfy two conditions in order to be defined
as a SUPAPolicyTarget. First, the set of managed entities that are
to be affected by the SUPAPolicy must all agree to play the role of
a SUPAPolicyTarget. In general, a managed entity may or may not be
in a state that enables SUPAPolicies to be applied to it to change
its state; hence, a negotiation process may need to occur to enable
the SUPAPolicyTarget to signal when it is willing to have
SUPAPolicies applied to it. Second, a SUPAPolicyTarget must be able
to process (directly or with the aid of a proxy) SUPAPolicies.
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If a proposed SUPAPolicyTarget meets both of these conditions, it
SHOULD set its supaPolicyTargetEnabled Boolean attribute to a
value of TRUE.
A SUPAPolicyTarget SHOULD be mapped to a role (e.g., using the
role-object pattern). This enables role-based access control to
be used to restrict which entities can author a given policy.
Note that Role is a type of SUPAPolicyMetadata.
5.15.1. SUPAPolicyTarget Attributes
Currently, no attributes are defined for the SUPAPolicyTarget
class.
5.15.2. SUPAPolicyTarget Relationships
SUPAPolicyTarget participates in a single relationship,
SUPAHasPolicyTarget, as defined in section 5.3.2.3.
5.16. The Abstract Class "SUPAPolicyMetadata"
Metadata is information that describes and/or prescribes
characteristics and behavior of another object that is **not**
an inherent, distinguishing characteristic or behavior of that
object (otherwise, it would be an integral part of that object).
For example, a socialSecurityNumber attribute should not be part
of a generic Person class. First, most countries in the world do
not know what a social security number is, much less use them.
Second, a person is not created with a social security number;
rather, a social security number is used to track people for
administering social benefits, though it is also used as a form
of identification.
Continuing the example, a better way to add this capability to a
model would be to have a generic Identification class, then
define a SocialSecurityNumber subclass, populate it as necessary,
and then define a composition between a Person and it (this is a
composition because social security numbers are not reused).
Since social security numbers are given to US citizens, permanent
residents, and temporary working residents, and because it is
also used to administer benefits, the composition is realized
as an association class to define how it is being used.
An example of descriptive metadata for network elements would be
documentation about best current usage practices (this could also
be in the form of a reference). An example of prescriptive
metadata for network elements would be the definition of a time
period during which specific types of operations are allowable.
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This is an optional class that defines the top of a hierarchy of
model elements that are used to define different types of metadata
that can be applied to policy and policy component objects. This
enables common metadata to be defined as objects and then reused
when the metadata are applicable. One way to control whether
SUPAPolicyMetadata objects are reused is by using the attributes
of the SUPAHasPolicyMetadataDetail association class.
It is recommended that this class, along with its
SUPAPolicyConcreteMetadata and SUPAPolicyMetadataDecorator
subclasses, be used as part of a conformant implementation. It is
defined to be optional, since metadata is not strictly required.
However, metadata can help specify and describe SUPAPolicyObject
entities, and can also be used to drive dynamic behavior.
5.16.1. SUPAPolicyMetadata Attributes
This section defines the attributes of the SUPAPolicyMetadata
class.
5.16.1.1. The Attribute "supaPolMetadataDescription"
This is an optional string attribute that defines a free-form
textual description of this metadata object.
5.16.1.2. The Attribute "supaPolMetadataIDContent"
This is a mandatory string attribute that represents part of the
object identifier of an instance of this class. It defines the
content of the object identifier. It works with another class
attribute, called supaPolMetadataIDEncoding, which defines how to
interpret this attribute. These two attributes form a tuple,
and together enable a machine to understand the syntax and value
of an object identifier for the object instance of this class.
5.16.1.3. The Attribute "supaPolMetadataIDEncoding"
This is an optional non-zero enumerated integer attribute that
represents part of the object identifier of an instance of this
class. It defines the format of the object identifier. It works
with another class attribute, called supaPolMetadataIDContent,
which defines the content of the object ID.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of an object identifier for
the object instance of this class. The supaPolMetadataIDEncoding
attribute is mapped to the following values:
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0: undefined
1: GUID
2: UUID
3: URI
4: FQDN
5.16.1.4. The Attribute "supaPolMetadataName"
This is an optional string attribute that defines the name of this
SUPAPolicyMetadata object.
5.16.2. SUPAPolicyMetadata Relationships
SUPAPolicyMetadata participates in a single aggregation, which is
defined in the following subsections.
5.16.2.1. The Aggregation "SUPAHasPolicyMetadata"
This is an optional aggregation that defines the set of
SUPAPolicyMetadata that are aggregated by this particular
SUPAPolicyObject. It is recommended that this aggregation be used
as part of a conformant implementation.
The multiplicity of this relationship is defined as 0..n on the
aggregate (SUPAPolicyObject) side, and 0..n on the part
(SUPAPolicyMetadata) side. This means that this relationship is
optional. The semantics of this aggregation are implemented using
the SUPAHasPolicyMetadataDetail association class.
5.16.2.2. The Abstract Class "SUPAHasPolicyMetadataDetail"
This is an optional abstract association class, and defines the
semantics of the SUPAHasPolicyMetadata aggregation. Its purpose is
to determine which SUPAPolicyMetadata object instances should be
attached to which particular object instances of the
SUPAPolicyObject class. This is done by using the attributes and
relationships of the SUPAPolicyMetadataDetail class to constrain
which SUPAPolicyMetadata objects can be aggregated by which
particular SUPAPolicyObject instances. It is recommended that this
association class be used as part of a conformant implementation.
5.16.2.2.1. The Attribute "supaPolMetadataIsApplicable"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then the SUPAPolicyMetadata object(s) of this
particular SUPAHasPolicyMetadata aggregation SHOULD be aggregated
by this particular SUPAPolicyObject.
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5.16.2.2.2. The Attribute "supaPolMetadataConstraintEncoding"
This is an optional non-negative enumerated integer that defines
how to interpret each string in the supaPolMetadataConstraint
class attribute. Values include:
0: undefined
1: OCL 2.4
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
Enumerations 1-3 are dedicated to OCL (with OCL 2.4 being the
latest version as of this writing). QVT defines a set of languages
(the two most powerful and useful are defined by enumerations 4
and 5). Alloy is a language for describing constraints, and uses a
SAT solver to guarantee correctness.
If this class is instantiated, then this attribute SHOULD also be
instantiated, and should be part of a conformant implementation.
5.16.2.2.3. The Attribute "supaPolMetadataConstraint[0..n]"
This is an optional array of string attributes. Each attribute
specifies a constraint to be applied using the format identified
by the value of the supaPolMetadataPolicyConstraintEncoding class
attribute. This provides a more rigorous and flexible treatment of
constraints than is possible in [RFC3460].
If this class is instantiated, then this attribute SHOULD also be
instantiated, and should be part of a conformant implementation.
Note: [0..n] means that this is a multi-valued property that has
zero or more attributes.
5.17. The Concrete Class "SUPAPolicyConcreteMetadata"
This is an optional concrete class. It defines an object that will
be wrapped by concrete instances of the SUPAPolicyMetadataDecorator
class. It can be viewed as a "carrier" for metadata that will be
attached to a subclass of SUPAPolicyObject. Since the decorator
pattern is used, any number of concrete subclasses of the
SUPAPolicyMetadataDecorator class can wrap an instance of the
SUPAPolicyConcreteMetadata class.
It is recommended that this class be used as part of a conformant
implementation.
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5.17.1. SUPAPolicyConcreteMetadata Attributes
Currently, two attributes are defined for the
SUPAPolicyConcreteMetadata class, and are described in the
following subsections.
5.17.1.1. The Attribute "supaPolMDValidPeriodEnd"
This is an optional attribute. Its data type should be able to
express a date and a time. This attribute defines the ending
date and time that this Metadata object is valid for.
5.17.1.2. The Attribute "supaPolMDValidPeriodStart"
This is an optional attribute. Its data type should be able to
express a date and a time. This attribute defines the starting
date and time that this Metadata object is valid for.
5.17.2. SUPAPolicyConcreteMetadata Relationships
This class inherits the relationships of the SUPAPolicyMetadata
class; see section 5.16.2. It can also be used by subclasses of
the SUPAPolicyMetadataDecorator class, and hence, can participate
in the HasSUPAMetadataDecorator aggregation; see section 5.18.2.
5.18. The Abstract Class "SUPAPolicyMetadataDecorator"
This is an optional class, and is used to implement the decorator
pattern (see section 5.7.1.) for metadata objects. This pattern
enables all or part of one or more SUPAPolicyMetadataDecorator
subclasses to "wrap" a SUPAPolicyConcreteMetadata object instance.
It is recommended that this class be used as part of a conformant
implementation.
5.18.1. SUPAPolicyMetadataDecorator Attributes
Currently, no attributes are defined for the
SUPAPolicyMetadataDecorator class.
5.18.2. SUPAPolicyMetadataDecorator Relationships
This class inherits the relationships of the SUPAPolicyMetadata
class; see section 5.16.2. It also defines a single aggregation,
HasSUPAMetadataDecorator, which is used to implement the decorator
pattern, as described in the following subsections.
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5.18.2.1. The Aggregation "HasSUPAMetadataDecorator"
This is an optional aggregation, and is part of a decorator
pattern. It is used to enable a concrete instance of a
SUPAPolicyMetadataDecorator to dynamically add behavior to a
SUPAPolicyConcreteMetadata object instance. The semantics of this
aggregation are defined by the HasSUPAMetadataDecoratorDetail
association class.
It is recommended that this aggregation be part of a conformant
implementation.
The multiplicity of this aggregation is 0..1 on the aggregate
(SUPAPolicyMetadataDecorator) side and 1..n on the part
(SUPAPolicyMetadata) side. This means that if this aggregation is
defined, then at least one SUPAPolicyMetadata object (e.g., a
concrete subclass of SUPAPolicyMetadataDecorator) must also be
instantiated and wrapped by this SUPAPolicyConcreteMetadata object
instance. The semantics of this aggregation are defined by the
HasSUPAMetadataDecoratorDetail association class.
5.18.2.2. The Association Class "HasSUPAMetadataDecoratorDetail"
This is an optional concrete association class, and defines the
semantics of the HasSUPAMetadataDecorator aggregation. The purpose
of this class is to use the Decorator pattern to determine
which SUPAPolicyMetadataDecorator object instances, if any, are
required to augment the functionality of the
SUPAPolicyConcreteMetadata object instance that is being used.
It is recommended that this association class be part of a
conformant implementation.
Attributes for this association class will be defined in a future
version of this document.
5.19. The Concrete Class "SUPAPolicyAccessMetadataDef"
This is an optional concrete class that defines access control
information, in the form of metadata, that can be added to a
SUPAPolicyObject. This is done using the SUPAHasPolicyMetadata
aggregation (see section 5.2.2.). This enables all or part of a
standardized description and/or specification of access control
for a given SUPAPolicyObject to be easily changed at runtime by
wrapping an object instance of the SUPAPolicyConcreteMetadata
class (or its subclass) with all or part of this object, and then
adorning the SUPAPolicyObject with the SUPAPolicyConcreteMetadata
object instance.
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5.19.1. SUPAPolicyAccessMetadataDef Attributes
Currently, the SUPAPolicyAccessMetadataDef class defines three
attributes; these are described in the following subsections.
5.19.1.1. The Attribute "supaPolAccessPrivilegeDef"
This is an optional non-negative enumerated integer attribute. It
specifies the access privileges that external Applications have
when interacting with a specific SUPAPolicyObject that is adorned
with an instance of this SUPAPolicyAccessMetadataDef object. This
enables the management system to control, in a consistent manner,
the set of operations that external Applications have for
SUPAPolicies and components of SUPAPolicies. Values include:
0: undefined
1: read only (for all policy components)
2: read and write (for all policy components)
3: privileges are specified by an external MAC model
4: privileges are specified by an external DAC model
5: privileges are specified by an external RBAC model
6: privileges are specified by an external ABAC model
7: privileges are specified by an external custom model
Values 1 and 2 apply to ALL SUPAPolicyObject instances that are
adorned with this SUPAPolicyConcreteMetadata object instance;
these two settings are "all-or-nothing" settings, and are included
for ease of use.
Values 3-7 indicate that a formal external access control model is
used. The name of this model, and its location, are specified in
two other class attributes, called supaPolAccessPrivilegeModelName
and supaPolAccessPrivilegeModelRef. MAC, DAC, RBAC, and ABAC
(values 3-6 stand for Mandatory Access Control, Discretionary
Access Control, Role-Based Access Control, and Attribute-Based
Access Control, respectively. A value of 7 indicates that a formal
external model that is not MAC, DAC, RBAC, or ABAC is used.
5.19.1.2. The Attribute "supaPolAccessPrivilegeModelName"
This is an optional string attribute that contains the name of
the access control model being used. If the value of the
supaPolAccessPrivilegeDef is 0-2, then the value of this attribute
is not applicable. Otherwise, the text in this class attribute
should be interpreted according to the value of the
supaPolAccessPrivilegeModelRef class attribute.
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5.19.1.3. The Attribute "supaPolAccessPrivilegeModelRef"
This is an optional non-negative enumerated integer attribute
that defines the data type of the supaPolAccessPrivilegeModelName
attribute. If the value of the supaPolAccessPrivilegeDef class
attribute is 0-2, then the value of this attribute is not
applicable. Otherwise, the value of this class attribute defines
how to interpret the text in the supaPolAccessPrivilegeModelRef
class attribute. Values include:
0: Undefined
1: URI
2: GUID
3: UUID
4: FQDN
5.20. The Concrete Class "SUPAPolicyVersionMetadataDef"
This is an optional concrete class that defines versioning
information, in the form of metadata, that can be added to a
SUPAPolicyObject. This enables all or part of a standardized
description and/or specification of version information for a
given SUPAPolicyObject to be easily changed at runtime by
wrapping an object instance of the SUPAPolicyConcreteMetadata
class (or its subclass) with all or part of this object.
5.20.1. SUPAPolicyVersionMetadataDef Attributes
Version information is defined in a generic format as follows:
<major>.<minor>.<relType>.<relTypeNum>
In this approach:
o supaVersionMajor denotes a major new release
o supaVersionMinor denotes an incremental release, that adds new
features and/or bug fixes to a major release
o supaVersionRelType denotes the type of release (e.g., internal,
alpha, production)
o supaVersionRelTypeNum denotes an incremental release of ability
particular type
Currently, the SUPAPolicyVersionMetadataDef class defines three
attributes; these are described in the following subsections.
5.20.1.1. The Attribute "supaVersionMajor"
This is an optional string attribute, and contains a string
(typically representing an integer) indicating a significant
increase in functionality is present in this version.
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5.20.1.2. The Attribute "supaVersionMinor"
This is an optional string attribute, and contains a string
(typically representing an integer) indicating that this release
contains a set of features and/or bug fixes that collectively do
not warrant incrementing the supaVersionMajor attribute. This
attribute should only be used if the supaVersionMajor attribute
is NOT NULL.
5.20.1.3. The Attribute "supaVersionRelType"
This is an optional integer attribute, and contains a string
defining the type of release of this SUPAPolicyObject. Values
include:
0: undefined
1: internal
2: alpha
3: beta
4: release candidate
5: production
6: maintenance
This attribute should only be used if the supaVersionMinor
attribute is NOT NULL.
5.20.1.4. The Attribute "supaVersionRelTypeNum"
This is an optional string attribute, and contains a string
defining the incremental release associated with the
supaVersionRelType class attribute. This attribute should only be
used if the supaVersionRelType attribute is NOT NULL.
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6. SUPA ECAPolicyRule Information Model
This section defines the classes, attributes, and relationships
of the SUPA ECAPolicyRule Information Model (EPRIM). Unless
otherwise stated, all classes (and attributes) defined in this
section were abstracted from DEN-ng [2], and a version of them are
in the process of being added to [5].
6.1. Overview
Conceptually, the EPRIM is a set of subclasses that specialize the
concepts defined in the GPIM for representing the components of a
Policy that uses ECA semantics. This is shown in Figure 23 (only
new EPRIM subclasses and their GPIM superclasses are shown).
(Class of another model that SUPA is integrating into)
|
+---SUPAPolicyObject (5.2)
|
+---SUPAPolicyStructure (5.3)
| |
| +---SUPAECAPolicyRule (6.4)
| |
| +---SUPAECAPolicyRuleAtomic (6.5)
| |
| +---SUPAECAPolicyRuleComposite (6.6)
|
+---SUPAPolicyComponentStructure (5.6)
|
+---SUPAPolicyClause (5.7)
| |
| +---SUPABooleanClause (6.7)
| |
| +---SUPAECAPolicyRuleAtomic (6.8)
| |
| +---SUPAECAPolicyRuleComposite (6.9)
|
+---SUPAPolicyComponentDecorator (5.9)
|
+---SUPAECAComponent(6.10)
| |
| +---SUPAPolicyEvent (6.11)
| |
| +---SUPAPolicyCondition (6.12)
| |
| +---SUPAPolicyAction (6.13)
Figure 23. The EPRIM Class Hierarchy
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Specifically, the EPRIM specializes the SUPAPolicyStructure class
class to create a SUPAECAPolicyRule (see sections 6.4 - 6.6); it
also specializes two subclasses of the SUPAPolicyComponentStructure
class to create two new sets of policy components. These two
SUPAPolicyComponentStructure subclasses are:
o a new subclass of SUPAPolicyClause, called SUPABooleanClause
(see sections 6.7 - 6.9), is defined for constructing Boolean
clauses that are specific to the needs of ECA Policy Rules
o a new subclass of SUPAPolicyComponentDecorator, called
SUPAECAComponent (see sections 6.10 - 6.13), is defined for
constructing reusable objects that represent Events,
Conditions, and Actions
The EPRIM provides new functionality, based on the GPIM, by
extending the GPIM to define new classes and relationships. The
EPRIM does NOT define new classes that are not inherited from
existing GPIM classes. This ensures that the semantics of the GPIM
are not changed, even though new functionality (for ECA Policy
Rules and components) are being defined.
The overall strategy for refining the GPIM is as follows:
o SUPAECAPolicyRule is defined as a subclass of the GPIM
SUPAPolicyStructure class
o A SUPAECAPolicyRule has event, condition, and action clauses
o Conceptually, this can be viewed as three aggregations
between the SUPAECAPolicyRule and each clause
o Each aggregation uses an instance of a concrete subclass of
SUPAPolicyClause; this can be a SUPABooleanClause
(making it ECA-specific), a SUPAEncodedClause (making it
generic in nature), or a new subclass of SUPAPolicyClause
o Concrete subclasses of SUPAPolicyClause may be decorated
with zero or more concrete subclasses of the
SUPAPolicyComponentDecorator class
o An optional set of GPIM SUPAPolicySource objects can be
defined to represent the authoring of a SUPAECAPolicyRule
o An optional set of GPIM SUPAPolicyTarget objects can be
defined to represent the set of managed entities that will be
affected by this SUPAECAPolicyRule
o An optional set of SUPAPolicyMetadata can be defined for any
of the objects that make up a SUPAECAPolicyRule, including
any of its components
6.2. Constructing a SUPAECAPolicyRule
There are several different ways to construct a SUPAECAPolicyRule;
they differ in which set of components are used to define the
content of the SUPAECAPolicyRule, and whether each component is
decorated or not. The following are some examples of creating a
SUPAECAPolicyRule:
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o Define three types of SUPABooleanClauses, one each for the
event, condition, and action clauses that make up a
SUPAECAPolicyRule
o For one or more of the above clauses, associate an
appropriate set of SUPAPolicyEvent, SUPAPolicyCondition, or
SUPAPolicyAction objects, and complete the clause using an
appropriate SUPAPolicyOperator and a corresponding
SUPAPolicyValue or SUPAPolicyVariable
o Note that compound Boolean clauses may be formed using
one or more SUPABooleanClauseComposite objects with one or
more SUPABooleanClauseAtomic objects
o Define a SUPAPolicyCollection component, which is used to
aggregate a set of objects appropriate for a clause, and
complete the clause using an appropriate SUPAPolicyOperator
and a corresponding SUPAPolicyValue or SUPAPolicyVariable
o Create a new concrete subclass of SUPAPolicyComponentStructure
(i.e., a sibling class of SUPAPolicyComponentDecorator and
SUPAPolicyClause), and use this new subclass in a concrete
subclass of SUPABooleanClause; note that this approach enables
the new concrete subclass of SUPAPolicyComponentStructure to
optionally be decorated as well
o Create a new subclass of SUPAPolicyComponentDecorator (e.g.,
a sibling of SUPAECAComponent) that provides ECA-specific
functionality, and use that to decorate a SUPAPolicyClause
o Create a new concrete subclass of SUPAPolicyStructure that
provides ECA-specific functionality, and define all or part
of its content by aggregating a set of SUPAPolicyClauses
6.3. Working With SUPAECAPolicyRules
A SUPAECAPolicyRule is a type of SUPAPolicy. It is a tuple that
MUST have three clauses, defined as follows:
o The event clause defines a Boolean expression that, if TRUE,
triggers the evaluation of its condition clause (if the
event clause is not TRUE, then no further action for this
policy rule takes place).
o The condition clause defines a Boolean expression that, if
TRUE, enables the actions in the action clause to be executed
(if the condition clause is not TRUE, then no further action
for this policy rule takes place).
o The action clause contains a set of actions (note that an
action MAY invoke another SUPAECAPolicyRule; see section
6.13).
Each of the above clauses can be a simple Boolean expression (of
the form {variable operator value}, or a compound Boolean
expression consisting of Boolean combinations of clauses.
Compound Boolean expressions SHOULD be in CNF or DNF.
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Note that each of the above three clauses MAY have a set of
SUPAPolicyMetadata objects that can constrain, or otherwise
affect, how that clause is treated. For example, a set of
SUPAPolicyMetadata MAY affect whether none, some, or all actions
are executed, and what happens if an action fails.
Each of the three clauses can be constructed from either a
SUPAEncodedClause or a SUPABooleanClause. The advantage of using
SUPAEncodedClauses is simplicity, as the content of the clause is
encoded directly into the attributes of the SUPAEncodedClause. The
advantage of using SUPABooleanClauses is reusability, since each
term in each clause is potentially a reusable object.
Since a SUPABooleanClause is a subclass of a SUPAPolicyClause
(see Section 6.7), it can be decorated by one or more concrete
subclasses of SUPAPolicyComponentDecorator. Therefore, a
SUPAECAPolicyRule can be built entirely from objects defined in
the GPIM and EPRIM, which facilitates the construction of
SUPAPolicies by a machine.
The relation between a SUPAECAPolicyRule and a SUPAPolicyClause
is shown in Figure 24, and is explained in further detail in
Section 6.4.
SUPAHasPolicyClause
+----------------+------------------------+
| ^ |
| | |
/ \ | |
A | |
A \ / 0..1 | A 1..n \ /
+----------+-----------+ | +-----------+------+
| SUPAPolicyStructure | | | SUPAPolicyClause |
+----------+-----------+ | +-----------+------+
/ \ | / \
I A | |
I +----------+----------------+ |
I | SUPAHasPolicyClauseDetail | |
I +---------------------------+ |
I |
C I A |
+----------+----------+ +--------+----------+
| SUPAECAPolicyRule | | SUPABooleanClause |
+---------------------+ +-------------------+
Figure 24. SUPAECAPolicyRule Clauses
The SUPAHasPolicyClause aggregation is implemented using the
SUPAHasPolicyClauseDetail association class. These were
described in sections 5.4.2.1 and 5.4.2.2, respectively.
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6.4. The Abstract Class "SUPAECAPolicyRule"
This is a mandatory abstract class, which is a PolicyContainer
that aggregates PolicyEvents, PolicyConditions, PolicyActions into
a type of policy rule known as an Event-Condition-Action (ECA)
policy rule. As previously explained, this has the following
semantics:
IF the event clause evaluates to TRUE
IF the condition clause evaluates to TRUE
THEN execute actions in the action clause
ENDIF
ENDIF
The event clause, condition clause, and action clause collectively
form a three-tuple. Each clause MUST be defined by at least one
SUPAPolicyClause (which MAY be decorated with other elements,
as described in section 5.7).
Each of the three types of clauses is a 3-tuple of the form:
{variable operator value}
Each of the three clauses MAY be combined with additional clauses
using any combination of logical AND, OR, and NOT operators; this
forms a "compound" Boolean clause. For example, if A, B, and C are
three attributes in an event, then a valid event clause could be:
(A AND B) OR C
Note that the above expression is in DNF; the equivalent CNF form
is ((A OR C) AND (B OR C)). In either case, the output of all
three clauses is either TRUE or FALSE; this facilitates combining
and chaining SUPAECAPolicyRules.
An action clause MAY invoke a new SUPAECAPolicyRule; see section
6.13 for more details.
An ECAPolicyRule MAY be optionally augmented with PolicySources
and/or PolicyTargets (see sections 5.16 and 5.17, respectively).
In addition, all objects that make up a SUPAECAPolicyRule MAY
have SUPAPolicyMetadata (see section 5.16) attached to them to
further describe and/or specify behavior.
When defined in an information model, each of the event, condition,
and action clauses MUST be represented as an aggregation between a
SUPAECAPolicyRule (the aggregate) and a set of event, condition,
or action objects (the components). However, a data model MAY map
these definitions to a more efficient form (e.g., by flattening
these three types of object instances, along with their respective
aggregations, into a single object instance).
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The composite pattern [3] is applied to the SUPAECAPolicyRule
class, enabling its (concrete) subclasses to be used as either a
stand-alone policy rule or as a hierarchy of policy rules. This is
shown in Figure 25.
A
1..n +-------------------+
\| |
+--------------- + SUPAECAPolicyRule |
| /| |
| +--------+----------+
| / \
| SUPAHasECAPolicyRule I
| I
| I
| I
| +---------------+-------------+
| I I
/ \ I I
A I I
C \ / 0..1 I C I
+-----+---------+----------+ +-----------+-----------+
|SUPAECAPolicyRuleComposite| |SUPAECAPolicyRuleAtomic|
+--------------------------+ +-----------------------+
Figure 25. The Composite Pattern Applied to a SUPAECAPolicyRule
SUPAECAPolicyRuleComposite and SUPAECAPolicyRuleAtomic both
inherit from SUPAECAPolicyRule. This means that they are both
a type of SUPAECAPolicyRule. Hence, the HasSUPAECAPolicyRule
aggregation enables a particular SUPAECAPolicyRuleComposite
object to aggregate both SUPAECAPolicyRuleComposite as well as
SUPAECAPolicyRuleAtomic objects. In contrast, a
SUPAECAPolicyRuleAtomic can NOT aggregate either a
SUPAECAPolicyRuleComposite or a SUPAECAPolicyRuleAtomic.
SUPAECAPolicyRuleAtomic and SUPAECAPolicyRuleComposite are
defined in sections 6.5 and 6.6, respectively.
Note that the HasSUPAECAPolicyRule aggregation is defined by the
HasSUPAECAPolicyRuleDetail association class; both are defined
in sections 6.6.2 and 6.6.3, respectively.
6.4.1. SUPAECAPolicyRule Attributes
Currently, the SUPAECAPolicyRule defines two attributes, as
described in the following subsections.
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6.4.1.1. The Attribute "supaECAPolicyRulePriority"
This is a mandatory non-negative integer attribute that defines
the priority of this particular SUPAECAPolicyRule. A larger value
indicates a higher priority. A default value of 0 MAY be assigned.
Priority is used primarily for 2 reasons: (1) to resolve conflicts
among policy actions (e.g., given a set of conflicting actions,
which one will execute) and (2) to define the execution order of
policy actions (e.g., when one action may depend on the output of
one or more previous actions).
6.4.1.2. The Attribute "supaECAPolicyRuleStatus"
This is an optional non-negative enumerated integer whose value
defines the current status of this policy rule. Values include:
0: In development, not ready to be deployed
1: Ready to be deployed
2: Deployed but not enabled
3: Deployed and enabled, but not executed
4: Executed without errors
5: Executed with errors
6: Aborted during execution
6.4.2. SUPAECAPolicyRule Relationships
Currently, the SUPAECAPolicyRule does not define any
relationships. It inherits all four relationships defined by
the SUPAPolicyStructure class (see section 5.3.2.).
6.5. The Concrete Class "SUPAECAPolicyRuleAtomic"
This is a mandatory concrete class. This class is a type of
PolicyContainer, and represents a SUPAECAPolicyRule that can
operate as a single, stand-alone, manageable object. Put another
way, a SUPAECAPolicyRuleAtomic object can NOT be modeled as a set
of hierarchical SUPAECAPolicyRule objects; if this is required,
then a SUPAECAPolicyRuleComposite object should be used instead.
6.5.1. SUPAECAPolicyRuleAtomic Attributes
Currently, the SUPAECAPolicyRuleAtomic class does not define any
attributes.
6.5.2. SUPAECAPolicyRuleAtomic Relationships
Currently, the SUPAECAPolicyRuleAtomic class does not define any
relationships. It inherits all four relationships defined by the
SUPAPolicyStructure class (see section 5.3.2.).
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6.6. The Concrete Class "SUPAECAPolicyRuleComposite"
This is a mandatory concrete class. This class is a type of
PolicyContainer, and represents a SUPAECAPolicyRule as a hierarchy
of SUPAPolicy objects, where the hierarchy contains instances of a
SUPAECAPolicyRuleAtomic and/or SUPAECAPolicyRuleComposite objects.
Each of the SUPAPolicy objects, including the outermost
SUPAECAPolicyRuleComposite object, are separately manageable. More
importantly, each SUPAECAPolicyRuleComposite object represents an
aggregated object that is itself manageable.
6.6.1. SUPAECAPolicyRuleComposite Attributes
Currently, the SUPAECAPolicyRuleComposite defines one attribute,
as described in the following subsection.
6.6.1.1. The Attribute "supaECAEvalStrategy"
This is a mandatory, non-zero, integer attribute that enumerates
a set of allowable alternatives that define how the set of
SUPAECAPolicyRule object instances in a SUPAECAPolicyRuleComposite
object are evaluated. It is assumed that the event and condition
clauses of the SUPAECAPolicyRules have evaluated to TRUE (e.g., the
event has occurred and the conditions were met). Values include:
0: undefined
1: execute the first SUPAECAPolicyRule in the
SUPAECAPolicyRuleComposite and then terminate
2: execute only the highest priority SUPAECAPolicyRule(s) in
the SUPAECAPolicyRuleComposite and then terminate
3: execute all SUPAECAPolicyRules in prioritized order (if
any) regardless of whether their SUPAPolicyActions
succeed or fail
4: execute all SUPAECAPolicyRules in prioritized order (if
any) until at least one SUPAPolicyAction in a
SUPAECAPolicyRule fails, and then terminate
If the value of supaECAEvalStrategy is 3 or 4, then all
SUPAECAPolicyRules that have a priority will be executed first
(starting with the SUPAECAPolicyRule(s) that have the highest
priority, and descending); all SUPAECAPolicyRule(s) that do not
have a priority are then executed (in any order).
Assume that the actions in a given SUPAECAPolicyRuleComposite
are defined as follows
SUPAECAPolicyRule A, priority 0
SUPAECAPolicyRule B, priority 10
SUPAECAPolicyRule C, priority 5
SUPAECAPolicyRule D, priority 10
SUPAECAPolicyRule E, priority 2
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Then, if the supaECAEvalStrategy attribute value equals:
0: an error is issued
1: only SUPAECAPolicyRule A is executed
2: only SUPAECAPolicyRules B and D are executed
3: all SUPAECAPolicyRules are executed, regardless of any
failures in their SUPAPolicyActions
4: all SUPAECAPolicyRules are executed until a failure is
detected, and then execution for all SUPAECAPolicyRules
terminate
6.6.2. SUPAECAPolicyRuleComposite Relationships
Currently, the SUPAECAPolicyRuleComposite defines a single
aggregation between it and SUPAECAPolicyRule, as described below.
6.6.2.1. The Aggregation "SUPAHasECAPolicyRule"
This is an optional aggregation that implements the composite
pattern. The multiplicity of this aggregation is 0..1 on the
aggregate (SUPAECAPolicyRuleComposite) side and 1..n on the part
(SUPAECAPolicyRule) side. This means that if this aggregation
is defined, then at least one SUPAECAPolicyRule object (which may
be either an instance of a SUPAECAPolicyRuleAtomic or a
SUPAECAPolicyRuleComposite class) must also be instantiated and
aggregated by this particular SUPAECAPolicyRuleComposite object.
The semantics of this aggregation are defined by the
SUPAHasECAPolicyRuleDetail association class.
6.6.3. The Association Class "SUPAHasECAPolicyRuleDetail"
This is an optional association class, and defines the semantics
of the SUPHasECAPolicyRule aggregation. This enables the
attributes and relationships of the SUPAHasECAPolicyRuleDetail
class to be used to constrain which SUPHasECAPolicyRule objects
can be aggregated by this particular SUPAECAPolicyRuleComposite
object instance.
6.6.3.1. The Attribute "supaECAPolicyIsDefault"
This is an optional Boolean attribute. If the value of this
attribute is true, then this SUPAECAPolicyRule is a default
policy, and will be executed if no other SUPAECAPolicyRule
in the SUPAECAPolicyRuleComposite container has been executed.
This is a convenient way for error handling, though care should
be taken to ensure that only one default policy rule is defined
per SUPAECAPolicyRuleComposite container.
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6.7. The Abstract Class "SUPABooleanClause"
A SUPABooleanClause specializes a SUPAPolicyClause, and defines
a Boolean expression consisting of a standard structure in the
form of a SUPAPolicyVariable, a SUPAPolicyOperator, and a
SUPAPolicyValue. For example, this enables the following Boolean
clause to be defined:
Foo >= Baz
where 'Foo' is a PolicyVariable, '>=' is a PolicyOperator, and
'Baz' is a PolicyValue.
Note that in this approach, the SUPAPolicyVariable and
SUPAPolicyValue terms are defined as an appropriate subclass of
the SUPAPolicyComponentDecorator class; it is assumed that the
SUPAPolicyOperator is an instance of the SUPAPolicyOperator class.
This enables the EPRIM, in conjunction with the GPIM, to be used
as a reusable class library. This encourages interoperability,
since each element of the clause is itself an object defined by
the SUPA object hierarchy.
An entire SUPABooleanClause may be negated by setting the
supaBoolClauseIsNegated class attribute of the SUPABooleanClause
class to TRUE. Individual terms of a Boolean clause can be negated
by using the supaTermIsNegated Boolean attribute in the
SUPAPolicyTerm class (see section 5.10).
A PolicyClause is in Conjunctive Normal Form (CNF) if it is a
sequence of logically ANDed terms, where each term is a sequence
of logically ORed terms.
A PolicyClause is in Disjunctive Normal Form (DNF) if it is a
sequence of logically ORed terms, where each term is a sequence
of logically ANDed terms.
The construction of more complex clauses, which consist of a set
of simple clauses in CNF or DNF (as shown in the above example),
is provided by using the composite pattern [3] to construct two
concrete subclasses of the abstract SUPABooleanClause class. These
are called SUPABooleanClauseAtomic and SUPABooleanClauseComposite,
and are defined in sections 6.8 and 6.9, respectively. This
enables instances of either a SUPABooleanClauseAtomic and/or a
SUPABooleanClauseComposite to be aggregated into a
SUPABooleanClauseComposite object.
6.7.1. SUPABooleanClause Attributes
The SUPABooleanClause class currently defines one attribute,
which are defined in the following subsections.
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6.7.1.1. The Attribute "supaBoolClauseIsNegated"
This is a mandatory Boolean attribute. If the value of this
attribute is TRUE, then this (entire) SUPABooleanClause is
negated. Note that the supaPolTermIsNegated class attribute of
the SUPAPolicyTerm class is used to negate a single term.
6.7.2. SUPABooleanClause Relationships
Currently, no relationships are defined for the SUPABooleanClause
class. It inherits the relationships of SUPAPolicyClause (see
section 5.5.).
6.8. The Concrete Class "SUPABooleanClauseAtomic"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a single, stand-alone,
manageable object. A SUPABooleanClauseAtomic object can NOT be
modeled as a set of hierarchical clauses; if this functionality is
required, then a SUPABooleanClauseComposite object must be used.
Examples of Boolean clauses that could be contained in a
SUPABooleanClauseAtomic include P, NOT P, and (P OR Q), where P
and Q are literals (e.g., a variable name that can be either true
or false, or a formula that evaluates to a literal). Examples of
Boolean clauses that are NOT in CNF are NOT(P AND Q),
(P AND Q) OR R, and P AND (Q OR (R AND S)); their CNF equivalent
forms are NOT P AND NOT Q, (P AND R) OR (Q AND R), and
P AND (Q OR S) AND (Q OR S), respectively.
6.8.1. SUPABooleanClauseAtomic Attributes
No attributes are currently defined for the
SUPABooleanClauseAtomic class.
6.8.2. SUPABooleanClauseAtomic Relationships
Currently, no relationships are defined for the
SUPABooleanClauseAtomic class. It inherits the relationships of
SUPAPolicyClause (see section 5.5.).
6.9. The Concrete Class "SUPABooleanClauseComposite"
This is a mandatory concrete class that represents a
SUPABooleanClause that can operate as a hierarchy of PolicyClause
objects, where the hierarchy contains instances of
SUPABooleanClauseAtomic and/or SUPABooleanClauseComposite
objects. Each of the SUPABooleanClauseAtomic and
SUPABooleanClauseComposite objects, including the outermost
SUPABooleanClauseComposite object, are separately manageable.
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More importantly, each SUPAECAPolicyRuleComposite object
represents an aggregated object that is itself manageable.
Examples of Boolean clauses that could be contained in a
SUPABooleanClauseAtomic include ((P OR Q) AND R), and
((NOT P OR Q) AND (R OR NOT S) AND T), where P, Q, R, S, and
T are literals.
6.9.1. SUPABooleanClauseComposite Attributes
Two attributes are currently defined for the
SUPABooleanClauseComposite class, and are described in the
following subsections.
6.9.1.1. The Attribute "supaBoolClauseBindValue"
This is a mandatory non-zero integer attribute, and defines the
order in which terms bind to a clause. For example, the Boolean
expression "((A AND B) OR (C AND NOT (D OR E)))" has the following
binding order: terms A and B have a bind value of 1; term C has a
binding value of 2, and terms D and E have a binding value of 3.
6.9.1.2. The Attribute "supaBoolClauseIsCNF"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPABooleanClauseComposite is in CNF
form. Otherwise, it is in DNF form.
6.9.2. SUPABooleanClauseComposite Relationships
Currently, the SUPABooleanClauseComposite class defined a single
aggregation, which is described in the subsections below.
6.9.2.1. The Aggregation "SUPAHasBooleanClause"
This is a mandatory aggregation that defines the set of
SUPABooleanClause objects that are aggregated by this
SUPABooleanClauseComposite object.
The multiplicity of this relationship is 0..1 on the aggregate
(SUPABooleanClauseComposite) side, and 1..n on the part
(SUPABooleanClause) side. This means that one or more
SUPABooleanClauses are aggregated and used to define this
SUPABooleanClauseComposite object. The 0..1 cardinality on the
SUPABooleanClauseComposite side is necessary to enable
SUPABooleanClauses to exist (e.g., in a PolicyRepository) before
they are used by a SUPABooleanClauseComposite. The semantics of
this aggregation is defined by the SUPAHasBooleanClauseDetail
association class.
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6.9.3. The Concrete Class "SUPAHasBooleanClauseDetail"
This is a mandatory association class that defines the semantics
of the SUPAHasBooleanClause aggregation. This enables the
attributes and relationships of the SUPAHasBooleanClauseDetail
class to be used to constrain which SUPABooleanClause objects
can be aggregated by this particular SUPABooleanClauseComposite
object instance.
6.9.3.1. SUPAHasBooleanClauseDetail Attributes
The SUPAHasBooleanClauseDetail class currently does not define
any attributes at this time.
6.10. The Abstract Class "SUPAECAComponent"
This is a mandatory abstract class that defines three concrete
subclasses, one each to represent the concepts of reusable events,
conditions, and actions. They are called SUPAPolicyEvent,
SUPAPolicyCondition, and SUPAPolicyAction, respectively.
SUPAECAComponents provide two different ways to construct
SUPAPolicyClauses. The first is for the SUPAECAComponent to be
used as either a SUPAPolicyVariable or a SUPAPolicyValue, and the
second is for the SUPAECAComponent to contain the entire clause
text.
For example, suppose it is desired to define a policy condition
clause with the text 'queueDepth > 10'. The two approaches could
satisfy this as follows:
Approach #1 (canonical form):
SUPAPolicyCondition.supaPolicyConditionData contains the text
'queueDepth'
SUPAPolicyOperator.supaPolOpType is set to '1' (greater than)
SUPAPolicyValue.supaPolValContent is set to '10'
Approach #2 (SUPAECAComponent represents the entire clause):
SUPAPolicyCondition.supaPolicyConditionData contains the text
'queueDepth > 10'
The class attribute supaECACompIsTerm, defined in subsection
6.10.1.1, is used to identify which of these two approaches is
used by an object instance of this class.
6.10.1. SUPAECAComponent Attributes
A single attribute is currently defined for this class, and is
described in the following subsection.
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6.10.1.1. The Attribute supaECACompIsTerm
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPAECAComponent is used as the value
of a SUPAPolicyTerm to construct a SUPAPolicyClause (this is
approach #1 in section 6.10 above). If the value of this attribute
is FALSE, then this SUPAECAComponent contains the text of the
entire corresponding SUPAPolicyClause (this is approach #2 in
section 6.10 above).
6.10.2. SUPAECAComponent Relationships
No relationships are currently defined for this class.
6.11. The Concrete Class "SUPAPolicyEvent"
This is a mandatory concrete class that represents the concept of
an Event that is applicable to a policy management system. Such
an Event is defined as any important occurrence in time of a
change in the system being managed, and/or in the environment of
the system being managed. SUPAPolicyEvents can be used as part of
a SUPAPolicyClause; this is done by specifying the attribute name
and value of an Event in the supaPolicyEventData attribute of the
SUPAPolicyEvent. This enables event attributes to be used as part
of a SUPAPolicyClause.
Note: this class does NOT model the "raw" occurrences of Events.
Rather, it represents the concept of an Event object whose class
attributes describe pertinent attributes that can trigger the
evaluation of a SUPAECAPolicyRule.
6.11.1. SUPAPolicyEvent Attributes
Currently, five attributes are defined for the SUPAPolicyEvent
class, which are described in the following subsections.
6.11.1.1. The Attribute "supaPolicyEventIsPreProcessed"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPAPolicyEvent has been pre-
processed by an external entity, such as an Event Service Bus,
before it was received by the Policy Management System.
6.11.1.2. The Attribute "supaPolicyEventIsSynthetic"
This is an optional Boolean attribute. If the value of this
attribute is TRUE, then this SUPAPolicyEvent has been produced by
the Policy Management System. If the value of this attribute is
FALSE, then this SUPAPolicyEvent has been produced by an entity
in the system being managed.
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6.11.1.3. The Attribute "supaPolicyEventTopic[0..n]"
This is a mandatory array of string attributes, and contains the
subject that this PolicyEvent describes.
Note: [0..n] means that this is a multi-valued property that has
zero or more attributes.
6.11.1.4. The Attribute "supaPolicyEventEncoding"
This is a mandatory non-zero enumerated integer attribute, and
defines how to interpret the supaPolicyEventData class attribute.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of the data carried by the
object instance of this class. Values include:
0: Undefined
1: String
2: Integer
3: Boolean
4: Floating Point
5: DateTime
6.11.1.5. The Attribute "supaPolicyEventData[1..n]"
This is a mandatory attribute that defines an array of strings.
Each string in the array represents an attribute name and value
of an Event object. The format of each string is defined as
name:value. The 'name' part is the name of the SUPAPolicyEvent
attribute, and the 'value' part is the value of that attribute.
Note: [1..n] means that this is a multi-valued property that has
at least one (and possibly more) attributes. For example, if
this value of this attribute is:
{(startTime:0800), (endTime:1700)}
then this attribute contains two properties, called startTime and
endTime, whose values are 0800 and 1700, respectively.
Note that the supaPolicyEventEncoding class attribute defines how
to interpret the value portion of this attribute.
This attribute works with another class attribute, called
supaPolicyEventEncoding, which defines how to interpret this
attribute. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of the data carried
by the object instance of this class.
6.11.2. SUPAPolicyEvent Relationships
No relationships are currently defined for this class. It inherits
the relationships defined by the SUPAPolicyComponentDecorator (see
section 5.7.3.).
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6.12. The Concrete Class "SUPAPolicyCondition"
This is a mandatory concrete class that represents the concept of
an Condition that will determine whether or not the set of Actions
in the SUPAECAPolicyRule to which it belongs are executed or not.
SUPAPolicyConditions can be used as part of a SUPAPolicyClause
(e.g., var = SUPAPolicyCondition.supaPolicyConditionData) or as a
stand-alone SUPAPolicyClause (e.g., the supaPolicyConditionData
attribute contains text that defines the entire condition clause).
6.12.1. SUPAPolicyCondition Attributes
Currently, two attributes are defined for the SUPAPolicyCondition
class, which are described in the following subsections.
6.12.1.1. The Attribute "supaPolicyConditionData[1..n]"
This is a mandatory array of string attributes that contains the
content of this SUPAPolicyCondition object.
Note: [1..n] means that this is a multi-valued property that has
at least one (and possibly more) attributes.
This attribute works with another class attribute, called
supaPolicyConditionEncoding, which defines how to interpret this
attribute. These two attributes form a tuple, and together enable
a machine to understand the syntax and value of the data carried
by the object instance of this class.
6.12.1.2. The Attribute "supaPolicyConditionEncoding"
This is a mandatory non-zero enumerated integer attribute, and
defines the data type of the supaPolicyConditionData attribute.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of the content of this
SUPAPolicyCondition object. Values include:
0: undefined
1: String
2: OCL 2.x
3: OCL 1.x
4: QVT 1.2 - Relations Language
5: QVT 1.2 - Operational language
6: Alloy
6.12.2. SUPAPolicyEvent Relationships
No relationships are currently defined for this class. It inherits
the relationships defined by the SUPAPolicyComponentDecorator (see
section 5.7.3.).
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6.13. The Concrete Class "SUPAPolicyAction"
This is a mandatory concrete class that represents the concept of
an Action, which is a part of a SUPAECAPolicyRule, which may be
executed when both the event and the condition clauses of its
owning SUPAECAPolicyRule evaluate to true. The execution of this
action is determined by its SUPAECAPolicyRule container, and any
applicable SUPAPolicyMetadata objects. SUPAPolicyActions can be
used in three different ways:
o as part of a SUPAPolicyClause (e.g., var =
SUPAPolicyAction.supaPolicyActionData)
o as a stand-alone SUPAPolicyClause (e.g., the
supaPolicyActionData attribute contains text that defines
the entire action clause)
o to invoke a SUPAECAPolicyRule
In the third case, the execution semantics SHOULD be to suspend
the current execution of the set of SUPAPolicyActions that are
executing, transfer execution control to the invoked
SUPAECAPolicyRule, and resume the execution of the original set
of SUPAPolicyActions when the invoked SUPAECAPolicyRule has
finished execution.
6.13.1. SUPAPolicyAction Attributes
Currently, two attributes are defined for the SUPAPolicyCondition
class, which are described in the following subsections.
6.13.1.1. The Attribute "supaPolicyActionData[1..n]"
This is a mandatory array of string attributes that contains the
content of this SUPAPolicyAction object. This attribute works with
another class attribute, called supaPolicyActionEncoding, which
defines how to interpret this attribute. These two attributes form
a tuple, and together enable a machine to understand the syntax
and value of the data carried by the object instance of this class.
Note: [1..n] means that this is a multi-valued property that has
at least one (and possibly more) attributes.
Since this attribute could represent a term in a SUPAPolicyClause
(e.g., var = SUPAPolicyAction.supaPolicyActionData), a complete
SUPAPolicyClause (e.g., the supaPolicyActionData attribute
contains text that defines the entire action clause), or the
name of a SUPAECAPolicyRule to invoke, each element in the string
array is prepended with one of the following strings:
o 't:' (or 'term:'), to denote a term in a SUPAPolicyClause
o 'c:' (or 'clause:'), to denote an entire SUPAPolicyClause
o 'r:' (or 'rule:'), to invoke a SUPAECAPolicyRule
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6.13.1.2. The Attribute "supaPolicyActionEncoding"
This is a mandatory non-zero enumerated integer attribute, and
defines the data type of the supaPolicyActionData attribute. This
attribute works with another class attribute, called
supaPolicyActionData, which contains the content of the action.
These two attributes form a tuple, and together enable a machine
to understand the syntax and value of the content of this
SUPAPolicyAction object. Values include:
0: undefined
1: GUID
2: UUID
3: URI
4: FQDN
5: String
6: OCL 2.x
7: OCL 1.x
8: QVT 1.2 - Relations Language
9: QVT 1.2 - Operational language
10: Alloy
6.13.2. SUPAPolicyAction Relationships
No relationships are currently defined for this class. It inherits
the relationships defined by the SUPAPolicyComponentDecorator (see
section 5.7.3.).
Enumerations 1-4 are used to provide a reference to an action
object. Enumerations 5-10 are used to express the action to
perform as a string.
7. Examples
This will be defined in the next version of this document.
8. Security Considerations
This will be defined in the next version of this document.
9. IANA Considerations
This document has no actions for IANA.
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10. Acknowledgments
This document has benefited from reviews, suggestions, comments
and proposed text provided by the following members, listed in
alphabetical order: Andy Bierman, Bob Natale, Fred Feisullin,
Georgios Karagiannis, Liu (Will) Shucheng, Marie-Jose Montpetit.
11. References
This section defines normative and informative references for this
document.
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)",
RFC 6020, October 2010.
[RFC6991] Schoenwaelder, J., "Common YANG Data Types", RFC 6991,
July 2013.
11.2. Informative References
[RFC3060] Moore, B., Ellesson, E., Strassner, J., Westerinen,
A., "Policy Core Information Model -- Version 1
Specification", RFC 3060, February 2001
[RFC3198] Westerinen, A., Schnizlein, J., Strassner, J.,
Scherling, M., Quinn, B., Herzog, S., Huynh, A.,
Carlson, M., Perry, J., Waldbusser, S., "Terminology
for Policy-Based Management", RFC 3198, November, 2001
[RFC3460] Moore, B., ed., "Policy Core Information Model (PCIM)
Extensions, RFC 3460, January 2003
[1] Strassner, J., "Policy-Based Network Management",
Morgan Kaufman, ISBN 978-1558608597, Sep 2003
[2] Strassner, J., ed., "The DEN-ng Information Model",
add stable URI
[3] Riehle, D., "Composite Design Patterns", Proceedings
of the 1997 Conference on Object-Oriented Programming
Systems, Languages and Applications (OOPSLA '97).
ACM Press, 1997, Page 218-228
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[4] DMTF, CIM Schema, v2.44,
http://dmtf.org/standards/cim/cim_schema_v2440
[5] Strassner, J., ed., "ZOOM Policy Architecture and
Information Model Snapshot", TR235, part of the
TM Forum ZOOM project, October 26, 2014
[6] TM Forum, "Information Framework (SID), GB922 and
associated Addenda, v14.5,
https://www.tmforum.org/information-framework-sid/
[7] Liskov, B.H., Wing, J.M., "A Behavioral Notion of
subtyping", ACM Transactions on Programming languages
and Systems 16 (6): 1811 - 1841, 1994
[8] Klyus, M., Strassner, J., Liu, W., Karagiannis, G.,
Bi, J., "SUPA Value Proposition",
draft-klyus-supa-value-proposition-00, March 21, 2016
[9] ISO/IEC 10746-3 (also ITU-T Rec X.903), "Reference
Model Open Distributed Processing Architecture",
April 20, 2010
[10] Davy, S., Jennings, B., Strassner, J., "The Policy
Continuum - A Formal Model", Proc. of the 2nd Intl.
IEEE Workshop on Modeling Autonomic Communication
Environments (MACE), Multicon Lecture Notes, No. 6,
Multicon, Berlin, 2007, pages 65-78
[11] Gamma, E., Helm, R., Johnson, R., Vlissides, J.,
"Design Patterns - Elements of Reusable Object-Oriented
Software", Addison-Wesley, 1994, ISBN 0-201-63361-2
[12] Strassner, J., de Souza, J.N., Raymer, D., Samudrala,
S., Davy, S., Barrett, K., "The Design of a Novel
Context-Aware Policy Model to Support Machine-Based
Learning and Reasoning", Journal of Cluster Computing,
Vol 12, Issue 1, pages 17-43, March, 2009
[13] Liskov, B.H., Wing, J.M., "A Behavioral Notion of
subtyping", ACM Transactions on Programming languages
and Systems, 16 (6): 1811 - 1841, 1994
[14] Martin, R.C., "Agile Software Development, Principles,
Patterns, and Practices", Prentice-Hall, 2002,
ISBN: 0-13-597444-5
[15] Halpern, J., Strassner, J., "Generic Policy Data Model
for Simplified Use of Policy Abstractions (SUPA)"
draft-halpern-supa-generic-policy-data-model-00,
March 21, 2016
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Authors' Addresses
John Strassner
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95138 USA
Email: john.sc.strassner@huawei.com
Joel Halpern
Ericsson
P. O. Box 6049
Leesburg, VA 20178
Email: joel.halpern@ericsson.com
Jason Coleman
Cisco Systems
124 Copper Lake Lane
Georgetown Tx 78628
Email: routerjockey@me.com
Appendix A. Brief Analyses of Previous Policy Work
This appendix describes of some of the important problems with
previous IETF policy work., and describes the rationale for
taking different design decisions in this document.
A.1. PolicySetComponent vs. SUPAPolicyStructure
The ability to define different types of policy rules is not
present in [RFC3060] and [RFC3460], because both are based on [4],
and this ability is not present in [4]. [RFC3060], [RFC3460], and
[4] are all limited to CA (condition-action) policy rules. In
addition, events are NOT defined. These limitations mean that
RFC3060], [RFC3460], and [4] can only represent CA Policy Rules.
In contrast, the original design goal of SUPA was to define a
single class hierarchy that could represent different types of
policies (e.g., imperative and declarative). Hence, it was
decided to make SUPAPolicyStructure generic in nature, so that
different types of policies could be defined as subclasses. This
enables a single Policy Framework to support multiple types of
policies.
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A.2. Flat Hierarchy vs. SUPAPolicyComponentStructure
Figure 26 shows a portion of the class hierarchy of [RFC3460].
A
+--------+
| Policy |
+----+---+
/ \
|
|
+---------+------+------+------------+-----------+
| | | | |
A | | A | | A |
+-----+-----+ | +--------+--------+ | +------+-------+
| PolicySet | | | PolicyCondition | | | PolicyAction |
+-----+-----| | +--------+--------+ | +------+-------+
/ \ | / \ | / \
| | | | |
... | ... | ...
A | A |
+-------+--------+ +-------+-----+
| PolicyVariable | | PolicyValue |
+-------+--------+ +-------+-----+
/ \ / \
| |
... ...
Figure 26. Simplified Class Hierarcy of [RFC3460]
RFC3060], [RFC3460], and [4] defined PolicyConditions and
PolicyActions as subclasses of Policy (along with PolicySet,
which is the superclass of PolicyRules and PolicyGroups). This
means that there is no commonality between PolicyConditions and
PolicyActions, even though they are both PolicyRule components.
From an object-oriented point-of-view, this is incorrect, since a
PolicyRule aggregates both PolicyConditions and PolicyActions.
In addition, note that both PolicyVariables and PolicyValues are
siblings of PolicyRules, PolicyConditions, and PolicyActions. This
is incorrect for several reasons:
o a PolicyRule cannot rectly contain PolicyVariables or
PolicyValues, so they shouldn't be at the same level of the
class hierarchy
o both PolicyConditions and PolicyActions can contain
PolicyVariables and PolicyValues, which implies that both
PolicyVariables and PolicyValues should be lower in the
class hierarchy
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Note that in the current version of [4], PolicyVariable and
PolicyValue are both deleted. There are other changes as well,
but they are beyond the scope of this Appendix.
The original design goal of SUPA was to define a single class
hierarchy that could represent different types of policies and
policy components. This cannot be accomplished in [RFC3460], since
there is no notion of a policy component (or alternatively,
PolicyCondition, PolicyAction, PolicyVariable, and PolicyValue are
all components at the same abstraction level, which is clearly not
correct). Hence, SUPA defined the SUPAPolicyComponentStructure
class to capture the concept of a reusable policy component.
In summary, SUPAPolicyStructure subclasses define the structure of
a policy in a common way, while SUPAPolicyComponentStructure
subclasses define the content that is contained in the structure
of a policy, also in a common way.
A.3. PolicyRules and PolicyGroups vs. SUPAPolicyRules
A PolicySetComponent is an aggregation, implemented as an
association class, that "collects instances of PolicySet
subclasses into coherent sets of Policies". This is a recursive
aggregation, with multiplicity 0..n - 0..n, on the PolicySet
class.
Since this is a recursive aggregation, it means that a PolicySet
can aggregate zero or more PolicySets. This is under-specified,
and can be interpreted in one of two ways:
1. A PolicySet subclass can aggregate any PolicySet subclass
(PolicyRules can aggregate PolicyRules and PolicyGroups, and
vice-versa)
2. PolicyRules can aggregate PolicyRules, and PolicyGroups can
aggregate PolicyGroups, but neither class can aggregate the
other type of class
Both interpretations are ill-suited for policy-based management.
The problem with the first is that if PolicyGroup is the mechanism
for grouping, why can a PolicyRule aggregate a PolicyGroup? This
implies that PolicyGroups are not needed. The problem with the
second is that PolicyGroups cannot aggregate PolicyRules (which
again implies that PolicyGroups are not needed).
Furthermore, there are no mechanisms defined in the [RFC3460]
model to prevent loops of PolicyRules. This is a problem, because
EVERY PolicyRule and PolicyGroup inherits this recursive
aggregation.
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This is why this document uses the composite pattern. First, this
pattern clearly shows what object is aggregating what other
object (i.e., a SUPAECAPolicyRuleAtomic cannot aggregate ability
SUPAECAPolicyRuleComposite). Second, it does not allow ability
SUPAECAPolicyRule to be aggregated by another SUPAECAPolicyRule
(this is discussed more in the following subsection).
A.3.1. Sub-rules
Sub-rules (also called nested policy rules) enable a policy rule to
be contained within another policy rule. These have very complex
semantics, are very hard to debug, and provide limited value. They
also require a complex set of aggregations (see section A.4.).
The main reason for defining sub-rules in [RFC3460] is to enable
"complex policy rules to be constructed from multiple simpler
policy rules". However, the composite pattern does this much more
efficiently than a simple recursive aggregation, and avoids the
ambiguous semantics of a recursive aggregation. This latter point
is important, because if PolicyRule and/or PolicyGroup is
subclassed, then all subclasses still inherit this recursive
aggregation, along with its ambiguous semantics.
A.4. PolicyConditions and PolicyActions vs. SUPAECAComponent
There is no need to use the SimplePolicyCondition and
ComplexPolicyCondition objects defined in [RFC3460], since the
SUPAPolicyComponentStructure uses the decorator pattern (see
section 5.7) to provide more extensible types of conditions than is
possible with those classes. This also applies for the
SimplePolicyAction and the ComplexPolicyAction classes defined in
[RFC3460].
More importantly, this removes the need for a complex set of
aggregations (i.e., PolicyComponent, PolicySetComponent,
PolicyConditionStructure, PolicyConditionInPolicyRule,
PolicyConditionInPolicyCondition, PolicyActionStructure,
PolicyActionInPolicyRule, and PolicyActionInPolicyAction).
Instead, ANY SUPAECAComponent is defined as a decorator (i.e., a
subclass of SUPAPolicyComponentDecorator), and hence, Any
SUPAECAComponent is wrapped onto a concrete subclass of
SUPAPolicyClause using the SAME aggregation
(SUPAHasDecoratedPolicyComponent). This is a significantly simpler
design that is also more powerful.
A.5. The SUPAPolicyComponentDecorator Abstraction
One of the problems in building a policy model is the tendency to
have a multitude of classes, and hence object instances, to
represent different combinations of policy events, conditions, and
actions. This can lead to class and/or relationship explosion, as
is the case in [RFC3460], [4], and [6].
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For example, [RFC3460] defines five subclasses of PolicyCondition:
PolicyTimePeriodCondition, VendorPolicyCondition,
SimplePolicyCondition, CompoundPolicyCondition, and
CompoundFilterCondition. Of these:
o PolicyTimePeriodCondition is a data structure, not a class
o VendorPolicyCondition represents a condition using two
attributes that represent a multi-valued octet string
o SimplePolicyCondition, CompoundPolicyCondition, and
CompoundFilterCondition all have ambiguous semantics
SimplePolicyCondition represents an ordered 3-tuple, in the form
{variable, match, value}. However, the match operator is not
formally modeled. Specifically, "the 'match' relationship is to
be interpreted by analyzing the variable and value instances
associated with the simple condition". This becomes problematic
for several cases, such as shallow vs. deep object comparisons.
More importantly, this requires two separate aggregations
(PolicyVariableInSimplePolicyCondition and
PolicyValueInSimplePolicyCondition) to associate variables and
values to the SimplePolicyCondition, respectively. Since [RFC3460]
defines all relationships as classes, this means that the
expression "Foo > Bar" requires a total of FIVE objects (one each
for the variable and value, one for the SimplePolicyCondition, and
one each to associate the variable and value with the
SimplePolicyCondition).
This is exacerbated when SimplePolicyConditions are used to build
CompoundPolicyConditions. In addition to the above complexity
(which is required for each SimplePolicyCondition), a new
aggregation (PolicyConditionInPolicyCondition) is required to
aggregation PolicyConditions. Thus, the compound expression:
"((Foo > Bar) AND (Foo < Baz))" requires a total of THIRTEEN
objects (five for each of the terms being ANDed, plus one for the
CompoundPolicyCondition, and two to aggregate each term to the
CompoundPolicyCondition).
Note that in the above examples, the superclasses of each of the
relationships are omitted for clarity. In addition, [RFC3460] is
built using inheritance; this means that if a new function is
required, a new class must be built (e.g., CompoundFilterCondition
is a subclass, but all it adds is one attribute).
In constrast, the Decorator Pattern enables behavior to be
selectively added to an individual object, either statically or
dynamically, without having to build association classes. In
addition, the decorator pattern uses composition, instead of
inheritance, to avoid class explosion. This means that a new
variable, value, or even condition class can be defined at
runtime, and then all or part of that class can dynamically wrap
an existing object without need for recompilation and
redeployment.
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A.6. The Abstract Class "SUPAPolicyClause"
This abstraction is missing in [RFC3060], [RFC3460], [4], and [6].
SUPAPolicyClause was abstracted from DEN-ng [2], and a version of
this class is in the process of being added to [5]. However, the
class and relationship design in [5] differs significantly from
the corresponding designs in this document.
SUPAPolicyClause further reinforces the different between a policy
rule and a component of a policy rule by abstracting the content
of a policy rule as a reusable object. This is fundamental for
enabling different types of policy rules (e.g., imperative and
declarative) to to be represented using the same constructs.
A.7. Problems with the RFC3460 Version of PolicyVariable
The following subsections define a brief, and incomplete, set of
problems with the implementation of [RFC3460] (note that [RFC3060
did not define variables, operators, and/or values).
A.7.1. Object Bloat
[RFC3460] used two different and complex mechanisms for providing
generic get and set expressions. PolicyVariables were subclassed
into two subclasses, even though they performed the same semantic
function. This causes additional problems:
o PolicyExplicitVariables are for CIM compatibility; note that
the CIM does not contain either PolicyVariables or
PolicyValues ([4])
o PolicyImplicitVariable subclasses do not define attributes;
rather, they are bound to an appropriate subclass of
PolicyValue using an association
Hence, defining a variable is relatively expensive in [RFC3460],
as in general, two objects and an association must be used. The
objects themselves do not define content; rather, their names are
used as a mechanism to identify an object to match. This means
that an entire object must be used (instead of, for example, an
attribute), which is wasteful. It also make it difficult to
adjust constraints at runtime, since the constraint is defined in
a class that is statically defined (and hence, requires
recompilation and possibly redeployment if it is changed).
A.7.2. Object Explosion
The above three problems lead to class explosion (recall that in
[RFC3060], [RFC3460], and [4], associations are implemented as
classes).
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In contrast to this approach, the approach in this document keeps
the idea of the class hierarchy for backwards compatibility, but
streamlines the implementation. Specifically:
1. The decorator pattern is an established and very used
software pattern (it dates back to at least 1994 [11]).
2. The use of a single association class
(i.e., SUPAHasDecoratedPolicyComponentDetail) can represent
more constraints than is possible in the approaches of
[RFC3460] and [4] in a much more flexible manner, due to its
function as a decorator of other objects.
3. Note that there is no way to enforce the constraint matching
in [RFC3460] and [6]; the burden is on the developer to
check and see if the constraints specified in one class are
honored in the other class.
4. If these constraints are not honored, there is no mechanism
specified to define the clause as incorrectly formed.
A.7.3. Specification Ambiguities
There are a number of ambiguities in [RFC3460].
First, [RFC3460] says: "Variables are used for building individual
conditions". While this is true, variables can also be used for
building individual actions. This is reflected in the definition
for SUPAPolicyVariable.
Second, [RFC3460] says: "The variable specifies the property of a
flow or an event that should be matched when evaluating the
condition." While this is true, variables can be used to test many
other things than "just" a flow or an event. This is reflected in
the SUPAPolicyVariable definition.
Third, the [RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient.
Fourth, [RFC3460] is tightly bound to the DMTF CIM schema [4].
The CIM is a data model (despite its name), because:
o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
Fifth, the class hierarchy has two needless classes, called
SUPAImplicitVariable and SUPAExplicitVariable. These classes do
not define any attributes or relationships, and hence, do not
add any semantics to the model.
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Finally, in [RFC3460], defining constraints for a variable is
limited to associating the variable with a PolicyValue. This is
both cumbersome (because associations are costly; for example,
they equate to a join in a relational database management system),
and not scalable, because it is prone to proliferating PolicyValue
classes for every constraint (or range of constraints) that is
possible. Therefore, in SUPA, this mechanism is replaced with
using an association to an association class that defines
constraints in a much more general and powerful manner (i.e.,
the SUPAHasDecoratedPolicyComponentDetail class).
A.8. Problems with the RFC3460 Version of PolicyValue
The following subsections define a brief, and incomplete, set of
problems with the implementation of [RFC3460] (note that [RFC3060
did not define variables, operators, and/or values).
A.8.1. Object Bloat
[RFC3460] defined a set of 7 subclasses; three were specific to
networking (i.e., IPv4 Address, IPv6 Address, MAC Address) and 4
(PolicyStringValue, PolicyBitStringValue, PolicyIntegerValue, and
PolicyBooleanValue) were generic in nature. However, each of these
objects defined a single class attribute. This has the same two
problems as with PolicyVariables (see section 5.9.1.1):
1. Using an entire object to define a single attribute is very
wasteful and expensive
2. It also make it difficult to adjust constraints at runtime,
since the constraint is defined in a class that is statically
defined (and hence, requires recompilation and possibly
redeployment if it is changed).
A.8.2. Object Explosion
[RFC3460] definition requires the use of associations
in order to properly constrain the variable (e.g., define its
data type, the range of its allowed values, etc.). This is both
costly and inefficient (recall that in [RFC3060], [RFC3460], and
[4], associations are implemented as classes).
A.8.3. Lack of Constraints
There is no generic facility for defining constraints for a
PolicyValue. Therefore, there is no facility for being able to
change such constraints dynamically at runtime.
A.8.4. Tightly Bound to the CIM Schema
[RFC3460] is tightly bound to the DMTF CIM schema [4]. The CIM is
a data model (despite its name), because:
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o It uses keys and weak relationships, which are both concepts
from relational algebra and thus, not technology-independent
o It has its own proprietary modeling language
o It contains a number of concepts that are not defined in UML
(including overriding keys for subclasses)
A.8.5. Specification Ambiguity
[RFC3460] says: It is used for defining values and constants used
in policy conditions". While this is true, variables can also be
used for building individual actions. This is reflected in the
SUPAPolicyVariable definition.
A.8.6. Lack of Symmetry
Most good information models show symmetry between like components.
[RFC3460] has no symmetry in how it defines variables and values.
In contrast, this document recognizes that variables and values
are just terms in a clause; hence, the only difference in the
definition of the SUPAPolicyVariable and SUPAPolicyValue classes
is that the content attribute in the former is a single string,
whereas the content attribute in the latter is a string array.
In particular, the semantics of both variables and values are
defined using the decorator pattern, along with the attributes of
the SUPAPolicyComponentDecorator and the
SUPAHasDecoratedPolicyComponentDetail classes.
Appendix B. Mathematical Logic Terminology and Symbology
Appendix C. SUPA Logic Statement Information Model
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