| Network Working Group | P. Kewisch |
| Internet-Draft | Mozilla |
| Intended status: Standards Track | C. Daboo |
| Expires: July 10, 2018 | Apple, Inc. |
| M. Douglass | |
| RPI | |
| January 6, 2018 |
jCal: The JSON format for iCalendar
draft-ietf-jcardcal-jcal-01
This specification defines "jCal", a JSON format for iCalendar data.
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The iCalendar data format [RFC5545] is a widely deployed interchange format for calendaring and scheduling data. While many applications and services consume and generate calendar data, iCalendar is a specialized format that requires its own parser/generator. In contrast, JSON-based formats as defined in [RFC4627] are the native format for JavaScript widgets and libraries and it is appropriate to have a standard form of calendar data that is easier to work with than iCalendar.
The purpose of this specification is to define "jCal", a JSON format for iCalendar data. jCal is defined as a straightforward mapping into JSON from iCalendar, so that iCalendar data can be converted to JSON, and then back to iCalendar, without losing any semantic meaning in the data. Anyone creating jCal calendar data according to this specification will know that their data can be converted to a valid iCalendar representation as well.
The key design considerations are essentially the same as those for [RFC6321], that is:
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].
The underlying format used for jCal is JSON. Consequently, the terms "object" and "array" as well as the four primitive types are to be interpreted as described in Section 1 of [RFC4627].
Some examples in this document contain "partial" JSON documents used for illustrative purposes. In these examples, three periods "..." are used to indicate a portion of the document that has been removed for compactness.
This section describes how iCalendar data is converted to jCal using a simple mapping between the iCalendar data model and JSON elements.
iCalendar uses a line folding mechanism to limit lines of data to a maximum line length (typically 72 characters) to ensure maximum likelihood of preserving data integrity as it is transported via various means (e.g., email) - see Section 3.1 of [RFC5545]. Prior to converting iCalendar data into jCal all folded lines MUST be unfolded.
iCalendar data uses an "escape" character sequence for text values and property parameter values. When such text elements are converted into jCal the escaping MUST be removed. The only escaping that may be applied is any escaping mandated by JSON.
iCalendar uses a base64 encoding for binary data. However, it does not restrict the encoding from being applied to non-binary value types. So the following rules MUST be applied when processing a property with the "ENCODING" property parameter set to "BASE64":
When base64 encoding and decoding is used, it MUST conform to Section 4 of [RFC4648], which is the base64 method used in [RFC5545].
One key difference in the formatting of values used in iCalendar and jCal is that in jCal the specification uses date/time and utc-offset values aligned with the complete representation, extended format of [ISO.8601.2004].
At the top level of the iCalendar object model is an "iCalendar stream". This stream encompasses multiple "iCalendar objects". In jCal, the entire stream is represented by an array, where the first element is the string "icalendar" and subsequent elements are iCalendar objects represented as described in this document.
In the typical case where there is only one iCalendar object, encapsulation inside an "icalendar" array MAY be omitted.
An iCalendar stream can contain one or more iCalendar objects. Each iCalendar object, delimited by "BEGIN:VCALENDAR" and "END:VCALENDAR", is represented by a fixed length array with three elements:
The representation of an iCalendar object in JSON will be named "vcalendar component" throughout this document.
Example:
["icalendar",
["vcalendar",
[ /* properties */ ],
[ /* components */ ]
],
["vcalendar",
[ /* properties */ ],
[ /* components */ ]
],
...
]
iCalendar objects are comprised of a set of "components", "properties", "parameters" and "values". A "component" can contain other "components" or "properties". A "property" has a "value" and a set of zero or more "parameters".
An iCalendar object may contain a mix of iCalendar component types, for example vevent objects delimited by "BEGIN:VEVENT" and "END:VEVENT", task objects delimited by "BEGIN:VTODO" and "END:VTODO".
Each calendar component in the "VCALENDAR" object, delimited by "BEGIN" and "END", will be converted to a fixed length array with three fields that have a specific structure:
While the grouping of properties and sub-components does not retain the original order specified in the iCalendar stream, the semantics of a component are preserved.
The iCalendar to jCal component mapping is valid for both current iCalendar components and any new iCalendar components added in the future. Conversion is to be done in the same way.
Example:
["vevent", [ /* Array of jCal properties */ ], [ /* Array of jCal sub-components */ ] ]
iCalendar properties, whether they apply to the "VCALENDAR" object or to a component, are handled in a consistent way in the jCal format.
Each individual iCalendar property is represented in jCal by an array with three fixed elements, followed by at one or more additional elements, depending on if the property is a multi-value property as described in Section 3.1.2 of [RFC5545].
The array consists of the following fixed elements: Section 3.4.1.1 there can be any number of additional elements.
The remaining elements of the array are used for the value of the property. For single-value properties, the array MUST have exactly four elements, for multi-valued properties as described in
The array describing the property can then be inserted into the array designated for properties in any component, including the "vcalendar" component described in Section 3.3.
Example:
["vevent",
[
["summary", {}, "text", "Meeting with Fred"],
["categories", {}, "text", "Meetings", "Work"]
...
],
[ /* sub-components */ ]
]
The property parameters in the second element of the property array associate a set of parameter names with their respective value. Parameters are further described in Section 3.5.
To allow for a cleaner implementation, the parameter object MUST be present even if there are no parameters. In this case, an empty object MUST be used.
This section describes some properties that have special handling when converting to jCal.
Various iCalendar properties defined in [RFC5545], for example the "CATEGORIES" property, are defined as multi-valued properties. In jCal these properties are added as further members of the array describing the property.
Note that additional multi-valued properties may be added in extensions to the iCalendar format.
In iCalendar, the "GEO" property value is defined as a semi-colon separated list of two "FLOAT" values, the first representing latitude and the second longitude.
In jCal, the value for the "geo" property value is represented as an array of two values. The first value of the property represents the latitude, the second value represents the longitude.
When converting from jCal to iCalendar, the two values MUST be converted using a semi-colon as the separator character.
This kind of special casing can be seen as a "structured value", as described in [I-D.ietf-jcardcal-jcard], Section 3.3.1.3. Implementors may want to keep this in mind in case they aim to support both jCard and jCal in their product. For example, checking the data type of all property values instead of assuming an array for just GEO is RECOMMENDED. [CREF1]Make sure section is still valid when publishing final rfc
Example
["vevent",
[
["geo", {}, "float", [ 37.386013, -122.082932 ] ]
...
],
...
]
In iCalendar, the "REQUEST-STATUS" property value is defined as a semi-colon separated list of two or three "TEXT" values. The first represents a code, the second a description, and the third any additional data.
In jCal, the value for the "request-status" property value is represented as an array with two or three values. The first array element corresponds to the code, the second element corresponds to the description and the third element corresponds to the additional data. Each value is represented using a string value. If there is no additional data in the iCalendar value, the last element of the array SHOULD NOT be present.
This kind of special casing can be seen as a "structured value", as described in [I-D.ietf-jcardcal-jcard], Section 3.3.1.3. Implementors may want to keep this in mind in case they aim to support both jCard and jCal in their product. For example, checking the data type of all property values instead of assuming an array for just REQUEST-STATUS is RECOMMENDED. [CREF2]Make sure section is still valid when publishing final rfc
When converting from jCal to iCalendar, the two or three values MUST be converted using a semi-colon as the separator character.
Example:
["vevent":
[
["request-status", {}, "text", "2.0", "Success" ],
["request-status", {}, "text",
[
"3.7",
"Invalid Calendar User",
"ATTENDEE:mailto:jsmith@example.org"
]
],
...
],
...
]
Property parameters are represented as a JSON object where each key-value pair represents the iCalendar parameter name and its value. The name of the parameter MUST be in lowercase, the original case of the parameter value MUST be preserved.
Each individual iCalendar property parameter is represented in jCal by a key-value pair in the parameters object. The key uses the same name as the iCalendar property parameter, but in lowercase. For example, the "PARTSTAT" property parameter is represented in jCal by the "partstat" key. The case of the parameter value MUST be preserved.
Example:
["vevent":
[
["attendee",
{
"partstat": "ACCEPTED",
"rsvp": "TRUE",
"role": "REQ-PARTICIPANT"
},
"cal-address",
"mailto:jsmith@example.org"
],
["summary", {}, "text", "Meeting"],
...
],
...
]
iCalendar defines a "VALUE" property parameter (Section 3.2.20 of [RFC5545]). This property parameter MUST NOT be added to the parameters object. Instead, the value type is always explicitly mentioned in the third element of the array describing the property. Thus, when converting from iCalendar to jCal, any "VALUE" property parameters are skipped. When converting from jCal into iCalendar, the appropriate "VALUE" property parameter MUST be included in the iCalendar property if the value type is not the default value type for that property.
In [RFC5545], some parameters allow using a COMMA-separated list of values. To ease processing in jCal, the value of a parameter with multiple values MUST be represented in an array containing the separated values. The array elements MUST be string values. Single-value parameters SHOULD be represented using a single string value, but an array with one element MAY also be used. An example for a such parameter is the iCalendar "DELEGATED-FROM" and "DELEGATED-TO" parameter, more such parameters may be added in extensions.
DQUOTE characters used to encapsulate the separated values MUST NOT be added to the jCal parameter value.
Example 1:
...
["attendee",
{
"delegated-to": ["mailto:jdoe@example.org",
"mailto:jqpublic@example.org"]
},
"cal-address",
"mailto:jsmith@example.org"
],
...
Example 2:
...
["attendee",
{
"delegated-to": "mailto:jdoe@example.org"
},
"cal-address",
"mailto:jsmith@example.org"
],
...
The type of an iCalendar value is explicitly mentioned in the third element of the array describing a jCal property. The actual values of the property can be found in the fourth and following elements of the array.
...
["attach", {}, "binary", "SGVsbG8gV29ybGQh"],
...
...
["x-non-smoking", {}, "boolean", true],
...
...
["attendee", {}, "cal-address", "mailto:kewisch@example.com"],
...
...
["dtstart", {}, "date", "2011-05-17"],
...
...
["dtstart", {}, "date-time", "2012-10-17T12:00:00"],
["dtstamp", {}, "date-time", "2012-10-17T12:00:00Z"],
["dtend",
{ "tzid": "Europe/Berlin" },
"date-time",
"2011-10-17T13:00:00"
],
...
...
["duration", {}, "duration", "P1D"],
...
...
["x-grade", {}, "float", 1.3],
...
...
["percent-complete", {}, "integer", 42],
...
...
["freebusy",
{ "fbtype": "FREE" },
"period",
["1997-03-08T16:00:00Z", "P1D"]
],
...
...
["rrule",
{},
"recur",
{
"freq": "YEARLY",
"count": 5,
"byday": [ "-1SU", "2MO" ],
"bymonth": 10
}
],
...
...
["rrule",
{},
"recur",
{
"freq": "MONTHLY",
"interval": 2,
"bymonthday": [ 1, 15, -1 ],
"until": "2013-10-01"
}
],
...
...
["comment", {}, "text", "hello, world"],
...
...
["x-time-local", {}, "time", "12:30:00"],
["x-time-utc", {}, "time", "12:30:00Z"],
["x-time-offset", { "tzid": "Europe/Berlin" }, "time", "12:30:00"],
...
...
["tzurl", {}, "uri", "http://example.org/tz/Europe-Berlin.ics"],
...
...
["tzoffsetfrom", {}, "utc-offset", "-05:00"],
["tzoffsetto", {}, "utc-offset", "+12:45"],
..
iCalendar extension properties and property parameters (those with an "X-" prefix in their name) are handled in the same way as other properties and property parameters: the property is represented by an array, the property parameter represented by an object. The property or parameter name uses the same name as for the iCalendar extension, but in lowercase. For example, the "X-FOO" property in iCalendar turns into the "x-foo" jCal property. See Section 5 for how to deal with default values for unrecognized extension properties or property parameters.
When converting component, property and property parameter values, the names SHOULD be converted to uppercase. Although iCalendar names are case insensitive, common practice is to keep them all uppercase following the actual definitions in [RFC5545].
Backslash escaping and line folding MUST be applied to the resulting iCalendar data as required by [RFC5545].
Non-binary value types MUST NOT be base64 encoded.
jCal properties that do not specify the default type for the iCalendar property MUST add a VALUE parameter when converting to iCalendar. jCal properties that specify the default type SHOULD NOT add a VALUE parameter.
In iCalendar, properties have a default value type specified by their definition, e.g. "SUMMARY"'s value type is "TEXT" and "DURATION"'s is "DURATION". When a property uses its default value type, the "VALUE" property parameter does not need to be specified on the property.
When new properties are defined or "X-" properties used, an iCalendar to jCal converter might not recognize them, and not know what the appropriate default value types are, yet they need to be able to preserve the values. A similar issue arises for unrecognized property parameters. As a result, the following rules are applied when dealing with unrecognized properties and property parameters:
Example: The following is an example of an unrecognized iCalendar property (that uses a "DATE-TIME" value as its default), and the equivalent jCal representation of that property.
iCalendar:
X-PROPERTY:20110512T120000Z
jCal:
...
["x-property", {}, "text", "20110512T120000Z"],
...
Example: The following is an example of a jCal property (where the corresponding iCalendar property uses a "INTEGER" value as its default), and the equivalent iCalendar representation of that property.
jCal:
...
["percent-complete", {}, "integer", 95],
...
iCalendar:
PERCENT-COMPLETE:95
Example: The following is an example of an unrecognized iCalendar property parameter (that uses a "FLOAT" value as its default) specified on a recognized iCalendar property, and the equivalent jCal representation of that property and property parameter.
iCalendar:
DTSTART;X-PARAM=30.3;VALUE=DATE:20110512
jCal:
...
["dtstart", { "x-param": "30.3" }, "date", "2011-05-12"],
...
This section describes libraries known to implement this draft as per [I-D.sheffer-running-code].
Additionally, interoperability testing of this draft is an ongoing effort under members of calconnect, the Calendaring and Scheduling Consortium. CalDAV Vendors are looking into supporting this draft.
For security considerations specific to calendar data, see Section 7 of [RFC5545]. Since this specification is a mapping from iCalendar, no new security concerns are introduced related to calendar data.
The use of JSON as a format does have security risks. Section 7 of [RFC4627] discusses these risks.
This document defines a MIME media type for use with iCalendar in JSON data. This media type SHOULD be used for the transfer of calendaring data in JSON.
The authors would like to thank the following for their valuable contributions: William Gill, Erwin Rehme, and Dave Thewlis. This specification originated from the work of the XML-JSON technical committee of the Calendaring and Scheduling Consortium.
| [calconnect-artifacts] | The Calendaring and Scheduling Consortium, "Code Artifacts and Schemas" |
| [I-D.ietf-jcardcal-jcard] | Kewisch, P., "jCard: The JSON format for vCard", Internet-Draft draft-ietf-jcardcal-jcard-07, October 2013. |
| [I-D.sheffer-running-code] | Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: the Implementation Status Section", Internet-Draft draft-sheffer-running-code-06, June 2013. |
| [RFC4627] | Crockford, D., "The application/json Media Type for JavaScript Object Notation (JSON)", RFC 4627, DOI 10.17487/RFC4627, July 2006. |
Below is an ABNF schema as per [RFC5234] for iCalendar in JSON. ABNF Symbols not described here are taken from [RFC4627]. The schema is non-normative and given for reference only.
The numeric section numbers given in the comments refer to section in [RFC5545]. Additional semantic restrictions apply, especially regarding the allowed properties and sub-components per component. Details on these restrictions can be found in this document and [RFC5545].
Additional schemas may be available on the internet at [calconnect-artifacts].
; An iCalendar Stream is an array with the first element being the
; string "icalendar". All remaining elements are jcalobjects.
jcalstream = begin-array
DQUOTE "icalendar" DQUOTE
*(value-separator jcalobject)
end-array
; A jCal Object is a component with the component-name "vcalendar".
; Restrictions to which properties and sub-components may be
; specified are to be taken from RFC5545.
jcalobject = component
; A jCal component consists of the name string, properties array and
; component array
component = begin-array
DQUOTE component-name DQUOTE value-separator
properties-array value-separator
components-array
end-array
components-array = begin-array
[ component *(value-separator component) ]
end-array
; A jCal property consists of the name string, parameters object,
; type string and one or more values as specified in this document.
property = begin-array
DQUOTE property-name DQUOTE value-separator
params-object value-separator
DQUOTE type-name DQUOTE
propery-value *(value-separator property-value)
end-array
properties-array = begin-array
[ property *(value-separator property) ]
end-array
; Property values depend on the type-name. Aside from the value types
; mentioned here, extensions may make use of other JSON value types.
; The non-terminal symbol sructured-prop-value covers the special
; cases for GEO and REQUEST-STATUS
property-value = simple-prop-value / structured-prop-value
simple-prop-value = string / number / boolean
structured-prop-value =
begin-array
[ structured-element *(value-separator structured-element) ]
end-array
structured-element = simple-prop-value
; The jCal params-object is a JSON object which follows the semantic
; guidelines described in this document.
params-object = begin-object
[ params-member *(value-separator params-member) ]
end-object
params-member = DQUOTE param-name DQUOTE name-separator param-value
param-value = string / param-multi
param-multi = begin-array
[ string *(value-separtor string) ]
end-array
; The type MUST be a valid type as described by this document. New
; value types can be added by extensions.
type-name = "binary" / "boolean" / "cal-address" / "date" /
"date-time" / "duration" / "float" / "integer" /
"period" / "recur" / "text" / "time" / "uri" /
"utc-offset" / x-type
; Component, property, parameter and type names MUST be lowercase.
; Additional semantic restrictions apply as described by this
; document and RFC5545.
component-name = lowercase-name
property-name = lowercase-name
param-name = lowercase-name
x-type = lowercase-name
lowercase-name = 1*(%x61-7A / DIGIT / "-")
This section contains two examples of iCalendar objects with their jCal representation.
BEGIN:VCALENDAR CALSCALE:GREGORIAN PRODID:-//Example Inc.//Example Calendar//EN VERSION:2.0 BEGIN:VEVENT DTSTAMP:20080205T191224Z DTSTART:20081006 SUMMARY:Planning meeting UID:4088E990AD89CB3DBB484909 END:VEVENT END:VCALENDAR
["vcalendar",
[
["calscale", {}, "text", "GREGORIAN"],
["prodid", {}, "text", "-//Example Inc.//Example Calendar//EN"],
["version", {}, "text", "2.0"]
],
[
["vevent",
[
["dtstamp", {}, "date-time", "2008-02-05T19:12:24Z"],
["dtstart", {}, "date", "2008-10-06"],
["summary", {}, "text", "Planning meeting"],
["uid", {}, "text", "4088E990AD89CB3DBB484909"],
],
[]
]
]
]
BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Example Corp.//Example Client//EN BEGIN:VTIMEZONE LAST-MODIFIED:20040110T032845Z TZID:US/Eastern BEGIN:DAYLIGHT DTSTART:20000404T020000 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=4 TZNAME:EDT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 END:DAYLIGHT BEGIN:STANDARD DTSTART:20001026T020000 RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10 TZNAME:EST TZOFFSETFROM:-0400 TZOFFSETTO:-0500 END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20060206T001121Z DTSTART;TZID=US/Eastern:20060102T120000 DURATION:PT1H RRULE:FREQ=DAILY;COUNT=5 RDATE;TZID=US/Eastern;VALUE=PERIOD:20060102T150000/PT2H SUMMARY:Event #2 DESCRIPTION:We are having a meeting all this week at 12 pm fo r one hour\, with an additional meeting on the first day 2 h ours long.\nPlease bring your own lunch for the 12 pm meetin gs. UID:00959BC664CA650E933C892C@example.com END:VEVENT BEGIN:VEVENT DTSTAMP:20060206T001121Z DTSTART;TZID=US/Eastern:20060104T140000 DURATION:PT1H RECURRENCE-ID;TZID=US/Eastern:20060104T120000 SUMMARY:Event #2 bis UID:00959BC664CA650E933C892C@example.com END:VEVENT END:VCALENDAR
["vcalendar",
[
["prodid", {}, "text", "-//Example Corp.//Example Client//EN"],
["version", {}, "text", "2.0"],
],
[
["vtimezone",
[
["last-modified", {}, "date-time", "2004-01-10T03:28:45Z"],
["tzid", {}, "text", "US/Eastern"],
],
[
["daylight",
[
["dtstart", {}, "date-time", "2000-04-04T02:00:00"],
["rrule",
{},
"recur",
"FREQ=YEARLY;BYDAY=1SU;BYMONTH=4"
],
["tzname", {}, "text", "EDT"],
["tzoffsetfrom", {}, "utc-offset", "-05:00"],
["tzoffsetto", {}, "utc-offset", "-04:00"]
],
[]
],
["standard",
[
["dtstart", {}, "date-time", "2000-10-26T02:00:00"],
["rrule",
{},
"recur",
"FREQ=YEARLY;BYDAY=1SU;BYMONTH=10"
],
["tzname", {}, "text", "EST"],
["tzoffsetfrom", {}, "utc-offset", "-04:00"],
["tzoffsetto", {}, "utc-offset", "-05:00"]
],
[]
]
]
],
["vevent",
[
["dtstamp", {}, "date-time", "2006-02-06T00:11:21Z"],
["dtstart",
{ "tzid": "US/Eastern" },
"date-time",
"2006-01-02T12:00:00"
],
["duration", {}, "duration", "PT1H"],
["rrule", {}, "recur", "FREQ=DAILY;COUNT=5"],
["rdate",
{ "tzid": "US/Eastern" },
"period",
"2006-01-02T15:00:00/PT2H"
],
["summary", {}, "text", "Event #2"],
["description",
{},
"text",
// Note that comments and string concatenation are not
// allowed per JSON specification and is used here only
// to avoid long lines.
"We are having a meeting all this week at 12 pm for one " +
"hour, with an additional meeting on the first day 2 " +
"hours long.\nPlease bring your own lunch for the 12 pm " +
"meetings."
],
["uid", {}, "text", "00959BC664CA650E933C892C@example.com"]
],
[]
],
["vevent",
[
["dtstamp", {}, "date-time", "2006-02-06T00:11:21Z"],
["dtstart",
{ "tzid": "US/Eastern" },
"date-time",
"2006-01-02T14:00:00"
],
["duration", {}, "duration", "PT1H"],
["recurrence-id",
{ "tzid": "US/Eastern" },
"date-time",
"2006-01-04T12:00:00"
],
["summary", {}, "text", "Event #2"],
["uid", {}, "text", "00959BC664CA650E933C892C@example.com"]
],
[]
]
]
]