Internet DRAFT - draft-huangng-utid
draft-huangng-utid
Independent Submission N. G. Huang
Internet Draft Wuxi Institute of Technology
Intended status: Experimental May 19, 2015
Expires: November 2015
Universally Traceable Identifier (UTID)
draft-huangng-utid-05.txt
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Abstract
A Universally Traceable Identifier (UTID) is a compact string of
characters for identifying an abstract or physical object. A unique
feature of UTID is that it contains two types of forwarding messages
to achieve traceability. UTIDs are designed specially for Identifier
Tracing Protocol (ITDP) [I-D-IDTP].
This document defines the generic syntax of UTID, a generative
grammar for UTID, and the guidelines for their use, too.
Table of Contents
1. Introduction ................................................ 3
1.1. Overview of UTIDs ...................................... 3
1.2. Terminology ............................................ 4
1.3. UTIDs and URIs ......................................... 5
2. Conventions Used in This Document ............................ 5
3. Characters .................................................. 5
3.1. Reserved Characters ..................................... 6
3.2. Unreserved Characters ................................... 6
4. Syntax Components ........................................... 6
4.1. Dns .................................................... 6
4.2. Catalog ................................................ 6
4.3. Id ..................................................... 7
5. Formal Syntax ............................................... 7
5.1. UTID Syntax ............................................ 7
5.1.1. Maximum Length of UTIDs ............................ 7
5.1.2. Dns ............................................... 8
5.1.3. Catalog ........................................... 8
5.1.4. Id ................................................ 8
5.1.5. Nested UTID ....................................... 9
5.2. Reserved catalog ....................................... 9
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5.3. Examples ............................................... 9
6. Usage ...................................................... 10
6.1. Components Omitted .................................... 11
6.1.1. Catalog Omitted ................................... 11
6.1.2. Id Omitted ....................................... 11
6.1.3. Dns Only ......................................... 11
6.2. Without Dns ........................................... 11
6.3. Spaces ................................................ 12
6.4. Carrier of UTIDs ...................................... 12
6.5. Use of UTID ........................................... 12
7. Normalization and Comparison ................................ 13
8. Security Considerations .................................... 13
9. IANA Considerations ........................................ 13
10. Change log of this document ................................ 13
11. References ................................................ 14
11.1. Normative References .................................. 14
11.2. Informative References ................................ 15
12. Acknowledgments ........................................... 15
Appendix A. Parsing a UTID with a Regular Expression ........... 16
Appendix B. Delimiting a UTID in Context ....................... 17
1. Introduction
A Universal Traceable Identifier (UTID) provides a simple and
extensible means for identifying an abstract object and a physical
object. This specification of UTID syntax and semantic is derived
from concepts introduced by the Identifier Tracing Protocol (IDTP)
[I-D-IDTP], which is a communication protocol designed for tracing
an object and is initially presented in a reference [Huang2011]. The
syntax and semantic of UTID is designed to meet the requirements
needed for the operating of IDTP.
Note 1: This version of this document has an important change
compare to the previous version. The major change is the syntax of
UTID which has many influences on this document and IDTP protocol
[I-D-IDTP].
Note 2: A reference implementation, which is called "busilet", of
UTID and IDTP has been developed as open source software and could
be downloaded from http://sourceforge.net/projects/busilet/. For
more information please visit http://www.utid.org.
1.1. Overview of UTIDs
UTIDs are characterized as follows:
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o Universality: Universality provides several benefits. It allows
UTIDs to be used for different types of objects in various
contexts with same syntax. It allows UTIDs to be compatible with
preexisting identifiers defined in various existing
identification system.
o Traceability: UTIDs contain forwarding messages used by IDTP [I-
D-IDTP] to trace the origin of the information associated to the
objects identified by the UTIDs. There two types of forwarding
messages contained in UTID used by IDTP. This is a unique feature
of UTIDs and IDTP comparing to URIs and other communication
protocol. This is why a new identification system and
communication protocol are proposed.
o Identifier: An identifier embodies the information required to
distinguish what is being identified from all other objects
within its scope of identification.
A UTID is an identifier consisting of a sequence of characters
matching the syntax rule named <UTID> in Section 5.1. This
specification does not place any limits on the nature of an object.
UTIDs have a global scope and are interpreted consistently
regardless of context.
1.2. Terminology
This specification uses a number of terms related to UTID for
understanding the concept of UTID.
o Traceability: It refers to the ability to trace the history,
application or location of an entity by means of recorded
identifications [ISO8402]. The concept of entity in this document
is extended to abstract objects and physical objects.
o Object: It is refer to an abstract object or a physical object in
this document.
o IDTP: It is Identifier Tracing Protocol, as defined in reference
[I-D-IDTP]. UTIDs are designed specially for IDTP.
o UTID suffix: It is the last part of a UTID starting from a given
position.
o Tracing: It is the process to trace a request to its origin
server by forwarding the request. It is a special kind of
forwarding for the purpose of traceability.
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1.3. UTIDs and URIs
A UTID is similar to Uniform Resource Identifier (URI) defined by
RFC3986 [RFC3986]. URIs are uniform identifiers for general purposes.
UTIDs defined in this document are universal identifiers for IDTP
only. Their differences are as follows:
1. Traceability: A UTID contains two types of forwarding messages to
achieve traceability.
2. Syntax: The syntax is different from URIs. There are no percent-
encoding characters used to represent predefined delimiters in
components in UTIDs.
3. Nested: A UTID can nest another UTID as its component, even with
two or three nested levels, as long as the whole UTID is not
longer than 96 characters.
4. Usage: URIs are uniform identifiers for general purposes, while
UTIDs are universal identifiers designed for IDTP only.
UTIDs are not compatible with URIs because of the differences
described above. Therefore, UTIDs could not become a scheme under
URIs scheme architecture.
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 RFC-2119 [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 RFC-2119 significance.
This specification uses the terms "character" in accordance with the
definitions provided in [BCP19].
3. Characters
A UTID is composed from a set of characters consisting of digits,
letters, and graphic symbols. A reserved subset of those characters
may be used to delimit syntax components within a UTID while the
remaining characters, including both the unreserved set and those
reserved characters not acting as delimiters, define each
component's identifying data.
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3.1. Reserved Characters
UTIDs include components that are delimited by characters in the
"reserved" set. These characters are called "reserved" because they
are defined as delimiters by the UTID syntax.
reserved = "~" / "$"
3.2. Unreserved Characters
Characters that are allowed in a UTID but do not have a reserved
purpose are called unreserved. These include lowercase letters,
decimal digits, hyphen, and period.
unreserved = alpha / DIGIT / "-" / "."
alpha = %x61-7A ; a-z
4. Syntax Components
A UTID consists of three components referred to as the dns, catalog,
and id.
4.1. Dns
A dns component is the domain name in Domain Name System (DNS)
defined by RFC1034 and RFC1035 [RFC1034] [RFC1035] for who defines
the UTID and assigns the UTID to an object. It is required and MUST
NOT be empty (no characters).
The dns expresses one type of forwarding message of a UTID, which is
used directly by the TCP/IP network.
4.2. Catalog
There might be various ids in a dns of an organization. These ids
should be grouped into some catalogs. A catalog component expresses
the catalog message of the object identified by a UTID. It is not
required and may be empty (no characters).
The catalog message is used by IDTP to map a UTID to a set of data
format standard for communication, as defined in Section 6.2 of
reference [I-D-IDTP].
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4.3. Id
An id component is a string of characters for identifying an object.
It MUST be unique in the context defined by the catalog and dns
components. It may be a serial number, a unique string with meaning,
such as user name, or a unique number or string generated by machine.
It is not required but usually is not empty.
5. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) as described in RFC-5234 [RFC5234].
5.1. UTID Syntax
The UTID Syntax is as follows:
UTID = [ id ] "~" [ catalog ] "$" dns
id = 1 * 92 graphic
catalog = label 0 * 30 dot-label 0 * 1 label
dns = label 0 * 60 dot-label "." 2 * 7 alpha
label = alpha / DIGIT
dot-label = alpha / DIGIT / "-" / "."
alpha = %x61-7A ; a-z
graphic = %x21-7E / Graphic Unicode character
If one component (catalog) is empty, the delimiter ('~') before the
component SHOULD NOT be omitted.
5.1.1. Maximum Length of UTIDs
The maximum length of a UTID is 96 bytes including all delimiters in
the UTID although the sum of the maximum length of each components
is larger than 96. If one component is long, the other components
should be short to guarantee that the length of a UTID does not
exceed 96 bytes.
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5.1.2. Dns
The dns component MUST be a real DNS name registered in a domain
name registration agent and MUST NOT be an IP address or "localhost"
that is a loopback name of local machine. That is to say, there must
be at least one dot '.' in the dns component and the part after the
last dot must be a top-level domain.
The Domain Name System (DNS) [RFC1034] [RFC1035] defines the maximum
length of a DNS is 255. However, to simplify implementations, the
maximum length of a DNS used in UTID is limited to 64, which is
longer than nearly all DNS actually used in real world.
In the DNS definition, characters used in DNS may be lower case or
upper case without any significance attached to the case. However,
to simplify implementations, the characters used in dns component in
UTID MUST be lower case.
The Internationalizing Domain Names in Applications (IDNA) system
allows user applications, such as web browsers, map Unicode strings
into the valid DNS character set using Punycode, which is called
internationalized domain names. However, to simplify implementations,
internationalized domain names are not allowed in UTIDs.
5.1.3. Catalog
The catalog component consists of lowercase letters, decimal digits,
hyphen, and period only. A hyphen and a period should not be in the
beginning and ending position of the catalog component.
5.1.4. Id
Like catalog component, the id component consists of lowercase
letters, decimal digits, hyphen, and period. A hyphen and a period
should not be in the beginning and ending position of the catalog
component.
However, for the best compatibility, the id component may consists
of graphic characters, which include all graphic characters defined
in ISO/IEC 646 [ISO646] and all graphic characters defined in
Unicode [Unicode] except white space. The Unicode character SHOULD
be encoded in UTF-8 [STD63] character set.
The id component is case sensitive, while the catalog and dns
components support lower case only.
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It is recommended that id component use lowercase letters, decimal
digits, hyphen, and period only. The graphic characters are used
only for compatibility to existing code system purpose.
Space ('%x20') or any character less than %x20 is neither supported
by id component nor supported by the catalog and dns components in
UTIDs.
5.1.5. Nested UTID
A nested UTID is defined as the id component of a UTID is another
UTID. Therefore, the id component of a nested UTID MUST contain dns
component and follow the UTID syntax. On the contrary, a UTID in
which id component contains dns component is not necessary to be a
nested UTID. Whether a UTID is a nested UTID is determined both by
the syntax and the usage context of the UTID.
5.2. Reserved catalog
Some catalogs are reserved for future use. These catalogs include
'u', 'v' ,'w', 'x', 'y', and 'z', and all catalogs that end with
'.u', '.v' ,'.w', '.x', '.y', and '.z'.
5.3. Examples
Examples of UTIDs are as follows:
123~cat$abc.example
123~$abc.example
~cat$abc.example
~$abc.example
Examples of nested UTIDs are as follows:
123~cat$abc.example~log$zyx.example
123~cat$abc.example~$zyx.example
123~$abc.example~log$zyx.example
~$abc.example~$zyx.example
Examples of invalid UTIDs are as follows:
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123$abc.example
There is no ~ symbol in the string so that the 123 in the string is
ambiguous as id or catalog.
123~abc.example
There is no $ symbol in the string so that no dns could be defined.
cat$abc.example
There is no ~ symbol in the string.
$abc.example
There is no ~ symbol in the string.
123~abc$abcexample
The dns component is not a valid DNS.
123~abc$ABC.example
The dns component has a upper case letter.
Examples of invalid nested UTIDs are as follows:
123~$abc~$zyx.example
The is component is not a valid UTID because "abc" is not a valid
dns.
123~$abc.com$zyx.example
123$abc.test~$zyx.example
6. Usage
A UTID should be used as a whole. There is no concept such as
relative reference in URIs.
One or more components of UTIDs may be omitted (emppty), which are
discussed in following.
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6.1. Components Omitted
6.1.1. Catalog Omitted
The catalog component is used to map a UTID to a set of data format
standard for communication by IDTP.
If the catalog component is omitted, it means that default catalog
is used. The default catalog of a UTID is an empty string with
length of zero. There is always a catalog in a UTID in spite of
catalog component omitted or not, either explicitly defined by
catalog component in a UTID or implicitly defined by default catalog
of empty string.
6.1.2. Id Omitted
The id component is scarcely omitted. The id component may be
omitted in the following two cases:
o A UTID identifies all objects in the catalog specified in the
UTID.
o It does not concern the object that a UTID identifies. Therefore,
the UTID is used only as forwarding messages by IDTP.
6.1.3. Dns Only
Occasionally, a UTID consists of only dns component without id and
catalog components. In this case, both delimiter '~' and '$' SHOULD
NOT be omitted, catalog component is the default catalog of empty
string, and the id components are not the concerns.
The UTID of dns only is used only as forwarding messages by IDTP,
that is, the UTID refers to the origin server referred by dns only.
6.2. Without Dns
A UTID without dns component is invalid. However, UTIDs without dns
component may exist in some special usage context. Such UTIDs are
strictly limited to the interior of server and MUST NOT be
transmitted in communications.
For example, UTIDs are used as primary key in a database, which is a
typical usage of UTIDs. In this case, all the primary key values
have same dns component or even same catalog components. Therefore,
the redundant components are not necessary to be saved in the
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database and a mechanism of mapping primary key to UTID should be
established in the interior of server.
6.3. Spaces
Space ('%x20') or any character less than %x20 is neither supported
in id component nor the catalog and dns components in UTIDs.
It is acceptable for catalog components without supporting of space
character. However, it is occasionally happens that spaces character
occur in an id in existing identification system. In this case, the
spaces character should be replaced by some other visible characters
for compatibility, which is not defined in this document.
6.4. Carrier of UTIDs
UTIDs may be used in RFID or two dimension bar code as tags to
identify physical objects. UTIDs may also be used in a database as
primary keys or foreign keys to identify physical or abstract
objects. In such cases, the length of UTIDs is critical especially
in RFID and the data structure design of databases. To simplify
implementations, the maximum length of UTIDs is limited to 96 bytes.
If a UTID is used as a primary key in a database, the primary key
values usually are saved without dns component, or even without
catalog components and there should be a mechanism to convert the
primary keys to UTIDs in the server interior.
If a UTID is used as a foreign key in a database, the foreign key
values must be saved as whole UTIDs following the syntax of UTIDs.
There is no strict foreign key constraint to the referenced table.
In this case, the foreign key in a table usually refers to many
referenced tables distributed in many databases in local or remote
hosts, which are defined in the forwarding messages (dns and catalog
components) of UTIDs of foreign key values.
6.5. Use of UTID
The UTID may be used to identify any physical or conceptual thing in
the real world or conceptual world. For example, an UTID of
"101.room102~sensor$sample.test" indicate a sensor with number of
101 at room 102 in sample.test company.
The UTID is also compatible with existing code system. For example,
an ISBN of a book "9787111316275" may be coded in UTID as
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"9787111316275~isbn$id.cmpbook.com", where cmpbook.com is the
publisher of the book.
Another example is email address. An email of "test@gmail.com" may
be coded in UTID as "test@gmail.com~email$example.com".
A UTID can be read as "id of catalog in dns". For example, The UTID
"101~sensor$sample.test" can be read as "101 of sensor in
sample.test".
7. Normalization and Comparison
One of the most common operations on UTIDs is comparison to
determine whether two UTIDs are equivalent. All UTIDs are already
normalized so that the comparison of two UTIDs is case sensitive
comparison of them.
8. Security Considerations
This section is meant to inform application developers, information
providers, and users of the security limitations of UTID as
described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks.
Although a UTID does not in itself pose a security threat, but a
UTID is in plaintext transmitted over network without encryption.
Hence it exposes to any network sniffer tools and results in the
unintentional leakage of this information during the transferring
over network. There are some potential risks if id or catalog
components contain sensitive information. Therefore, it should be
careful to design the UTID components to avoid leakage of sensitive
information.
9. IANA Considerations
No IANA actions are required by this document.
10. Change log of this document
draft-huangng-utid-01: Add two links to the web site of reference
implementation of UTID and IDTP and official web site of UTID and
IDTP in the section "1. Introduction".
draft-huangng-utid-02: Add a section titled "6.5. Use of UTID"
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draft-huangng-utid-03: There is an important change. The syntax of
UTID is changed from id~cat@loc$dns to id~cat$dns. It causes many
changes in this document.
draft-huangng-utid-05: (1) No changes; (2) Just make the ID active.
11. References
11.1. Normative References
[BCP19] Freed, N. and J. Postel, "IANA Charset Registration
Procedures", BCP 19, RFC 2978, October 2000.
[ISO646] International Organization for Standardization (ISO),
"Information Technology: ISO 7-bit Coded Character Set for
Information Interchange", International Standard, Ref. No.
ISO/IEC 646:1991.
[ISO8402] International Organization for Standardization. ISO 8402:
1994: Quality Management and Quality Assurance-Vocabulary.
International Organization for Standardization, 1994.
[RFC1034] P. Mockapetris, "Domain names - concepts and facilities",
IETF RFC1034, Internet Eng. Task Force, Jan. 1987;
www.ietf.org/rfc/rfc1034.txt.
[RFC1035] P. Mockapetris, "Domain names - implementation and
specification", IETF RFC1035, Internet Eng. Task Force, Jan.
1987; www.ietf.org/rfc/rfc1035.txt.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] T. Berners-Lee, RT Fielding, and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", IETF RFC3986
(standards track), Internet Eng. Task Force, Jan. 2005;
www.ietf.org/rfc/rfc3986.txt.
[RFC5234] D. Crocker, Ed., "Augmented BNF for Syntax Specifications:
ABNF", IETF RFC5234 (standards track), Internet Eng. Task
Force, Jan. 2008; www.ietf.org/rfc/rfc5234.txt.
[STD63] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
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[Unicode] Julie D. Allen. The Unicode Standard, Version 6.0, The
Unicode Consortium, Mountain View, 2011.
11.2. Informative References
[Huang2011] Neng-Geng Huang, Bing-Liang Zhang, Zhi-Yuan Huang (2011):
"Concept and design of a things mail system", Signal
Processing, Communications and Computing (ICSPCC), 2011 IEEE
International Conference on. DOI: 10.1109/ICSPCC.2011.6061741
[I-D-IDTP] N. G. Huang, "Identifier Tracing Protocol (IDTP)",
Internet-Draft, draft-huangng-idtp-05.txt, May. 2015.
12. Acknowledgments
The author of this document thanks to Mr. Zhang Bing-Liang for his
innovative idea of things mail that inspired the concept of UTID and
IDTP.
This document was prepared using 2-Word-v2.0.template.dot.
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Appendix A. Parsing a UTID with a Regular Expression
The following line is the regular expression for breaking-down a
UTID into its components.
^([\u0021-\u007e\u0080-\uffff]{1,92})?~([a-z0-9][a-z0-9\-
\.]{0,30}[a-z0-9]?)?\$([a-z0-9][a-z0-9\-\.]{0,60}\.[a-z]{2,7})$
For example, matching the above expression to
123~cat$abc.example
results in the following sub expression matches:
$0 = 123~cat$abc.example
$1 = 123
$2 = cat
$3 = abc.example
Therefore, it can be determined that the three components are as
follows:
id = $1
catalog = $2
dns = $3
When above regular expression is used, any string that does not have
delimiters of '~' and '$' will cause an exception.
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Appendix B. Delimiting a UTID in Context
UTIDs are usually transmitted through formats that provide a clear
context for their interpretation. However, it is important to be
able to delimit the UTID from the rest of the text if a UTID is in a
plain text file for printing or transmitting. In such case, UTIDs
are delimited by double-quotes is recommended. For example,
"123$abc.example" is a UTID.
Copyright (c) 2015 IETF Trust and the persons identified as authors
of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
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Authors' Addresses
Neng Geng Huang
School of the Internet of Things
Wuxi Institute of Technology
Wuxi, Jiangsu,
China, 214121
Phone: 86-13921501950
Email: huangng@gmail.com
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