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Applications JSON data formats for vCard and iCalendar This specification defines "jCal", a JSON format for iCalendar data. The iCalendar data format is a text format for capturing and exchanging information normally stored within a calendaring and scheduling application, for example tasks and events. JSON is a lightweight, text-based, language-independent data interchange format commonly used in internet applications.

The iCalendar data format 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 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 , that is: Round-tripping (converting an iCalendar instance to jCal and back) will give the same semantic result as the starting point. For example, all components, properties and property parameters are guaranteed to be preserved. Ordering of elements and case of property and parameter names will not necessarily be preserved. The iCalendar data semantics are to be preserved, allowing a simple consumer to easily browse the data in jCal. A full understanding of iCalendar is still required in order to modify and/or fully comprehend the calendar data. Extensions to the underlying iCalendar specification must not lead to requiring an update to jCal.

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 . The underlying format used for jCal is JSON. Consequently, the terms "object" and "array" as well as the four primitive types (strings, numbers, booleans, and null) are to be interpreted as described in Section 1 of . 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. Aside from the formal description in this section, an informative ABNF is specified in . In , an iCalendar object comprises a set of "components", "properties", "parameters" and "values". The top level of iCalendar data typically contains a stream of iCalendar objects, each of which can be considered a "component". A "component" can contain other "components" or "properties". A "property" has a "value" and a set of zero or more "parameters". Each of these entities have a representation in jCal, defined in the following sections. The representation of a iCalendar object in JSON will be named "jCal object" throughout this document.

iCalendar uses a line folding mechanism to limit lines of data to a maximum line length (typically 75 octets) to ensure maximum likelihood of preserving data integrity as it is transported via various means (e.g., email) - see Section 3.1 of . iCalendar data uses an "escape" character sequence for text values and property parameter values. See Section 3.1 and 3.3 of as well as . There is a subtle difference in the number representations between JSON and iCalendar. While in iCalendar a number may have leading zeros, as well as a leading plus sign, this is not the case in JSON. Numbers should be represented in whatever way needed for the underlying format. When converting from iCalendar to jCal, first iCalendar lines MUST be unfolded. Afterwards, any iCalendar escaping MUST be unescaped. Finally JSON escaping, as described in Section 7, MUST be applied. The reverse order applies when converting from jCal to iCalendar, which is further described in . 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 are applied when processing a property with the "ENCODING" property parameter set to "BASE64": If the property value type is "BINARY", the base64 encoding MUST be preserved. If the value type is not "BINARY", the "ENCODING" property parameter MUST be removed, and the value MUST be base64 decoded. When base64 encoding and decoding is used, it MUST conform to Section 4 of , which is the base64 method used in . One key difference in the formatting of values used in iCalendar and jCal is that in jCal the specification uses date/time values aligned with the extended format of , which is more commonly used in internet applications that make use of the JSON format. The sections of this document describing the various date and time formats contain more information on the use of the complete representation, reduced accuracy or truncated representation.

At the top level of the iCalendar object model is an "iCalendar stream". This stream encompasses multiple "iCalendar objects". As the typical use case is transporting a single iCalendar object, there is no defined equivalent to an "iCalendar stream" in jCal. To transport multiple jCal objects in a stream, a simple JSON array can be used.

Example:

Each iCalendar component, delimited by "BEGIN" and "END", will be converted to a fixed length array with three fields that have a specific structure: A string with the name of the iCalendar component, but in lowercase. An array of jCal properties as described in . An array of jCal components, representing the sub-components of the component in question. This mapping applies to the top level iCalendar objects, as well as individual sub-components in the same way. 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. While the grouping of properties and sub-components does not retain the original order specified in the iCalendar data, the semantics of a component are preserved.

Example:

iCalendar properties, whether they apply to the "VCALENDAR" object or to a component, are handled in a consistent way in the jCal format. In jCal, each individual iCalendar property MUST be represented by an array with three fixed elements, followed by one or more additional elements, depending on if the property is a multi-value property as described in Section 3.1.2 of . The array consists of the following fixed elements: The name of the property, as a lowercase string. The iCalendar format specifies that property names are case-insensitive, and recommends that they be rendered in uppercase. In jCal, they MUST be in lowercase. An object containing the parameters as described in . If the property has no parameters, an empty object is used to represent that. The type identifier string of the value, in lowercase. Due to special casing of certain properties as described in , it is important that parsers check both the type identifier and the value data type and do not rely on assumptions based on the property name. The remaining elements of the array are used for one or more values of the property. For single-value properties, the array has exactly four elements; for multi-valued properties, as described in Section 3.1.2, each value is another element, and there can be any number of additional elements. In the following example, the "categories" property is multi-valued and has two values, while the summary property is single-valued:

Example:

This section describes some properties that have special handling when converting to jCal.

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, be careful to use a semi-colon as the separator between the two values as required by RFC5545. When converting from jCal to iCalendar, the two values MUST be converted using a semi-colon as the separator character.

Example

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. When converting from jCal to iCalendar, the two or three values MUST be converted using a semi-colon as the separator character.

iCalendar Example:

jCal Example:

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. For example, the "PARTSTAT" property parameter is represented in jCal by the "partstat" key. Any new iCalendar parameters added in the future will be converted in the same way.

Example:

iCalendar defines a "VALUE" property parameter (Section 3.2.20 of ). This property parameter MUST NOT be added to the parameters object. Instead, the value type is signaled through the type identifier in the third element of the array describing the property. When converting a property from iCalendar to jCal, the value type is determined as follows: If the property has a "VALUE" parameter, that parameter's value is used as the value type. If the property has no "VALUE" parameter but has a default value type, the default value type is used. If the property has no "VALUE" parameter and has no default value type, "unknown" is used. Converting from jCal into iCalendar is done as follows: If the property's value type is "unknown", no "VALUE" parameter is included. If the property's value type is the default type for that property, no "VALUE" parameter is included. Otherwise, a "VALUE" parameter is included, and the value type is used as the parameter value. See for information on handling unknown value types.

In , some parameters allow using a COMMA-separated list of values. To ease processing in jCal, the value of such parameters MUST be represented in an array containing the separated values. The array elements MUST be string values. Single-value parameters can be represented either using a single string value or an array with one string element. A jCal parser MUST be able to understand both value data types. An example for a such parameter is the iCalendar "DELEGATED-FROM" and "DELEGATED-TO" parameter, more such parameters may be added in extensions. The iCalendar specification requires encapsulation between DQUOTE characters if a parameter value contains a colon, a semicolon or a comma. These extra DQUOTE characters do not belong to the actual parameter value, and hence are not included when the parameter is converted to jCal.

Example 1:

Example 2:

The following subsections specify how iCalendar property value data types, which are defined in the subsections of Section 3.3, are represented in jCal.

iCalendar "BINARY" property values are represented by a property with type identifier "binary". The value element is a JSON string with base64 encoded data, conforming to Section 4 of , which is the base64 method used in .

iCalendar "BOOLEAN" property values are represented by a property with the type identifier "boolean". The value is a JSON boolean value.

iCalendar "CAL-ADDRESS" property values are represented by a property with the type identifier "cal-address". The value is a JSON string with the URI as described in .

iCalendar "DATE" property values are represented by a property with the type identifier "date". The value elements are JSON strings with the same date value specified by , but represented using the extended format of the complete representation specified in , Section 4.1.2.2. Other variations, for example representation with reduced accuracy, MUST NOT be used.

iCalendar "DATE-TIME" property values are represented by a property with the type identifier "date-time". The value elements are JSON strings with the same date value specified by , but represented using the extended format of the complete representation specified in , Section 4.3.2. Other variations, for example representation with reduced accuracy, MUST NOT be used. The same restrictions with respect to leap seconds and timezone offsets as specified in Section 3.3.5 apply.

iCalendar "DURATION" property values are represented by a property with the type identifier "duration". The value elements are JSON strings with the same duration value specified by .

iCalendar "FLOAT" property values are represented by a property with the type identifier "float". The value elements are JSON primitive number values.

vCard "INTEGER" property values are represented by a property with the type identifier "integer". The value elements are JSON primitive number values which MUST resolve to an integer value in the range specified in , Section 3.3.8. Thus a fractional and/or exponential part are only allowed under limited circumstances.

iCalendar "PERIOD" property values are represented by a jCal property with the type identifier "period". The value element is an array of JSON strings, with the first element representing the start of the period and the second element representing the end of the period. As in , the start of the period is always formatted as a date-time value and the end of the period MUST be either a date-time or duration value. Any date, date-time or duration values contained in the period value MUST be formatted in accordance to the rules for date, date-time or duration values specified in this document.

iCalendar "RECUR" property values are represented by a property with the type identifier "recur". The value elements are objects describing the structured data as specified by . Each rule part is described by the combination of key and value. The key specifies the name of the rule part and MUST be converted to lowercase. The value of the rule part MUST be mapped by the following rules: The value of the "freq" and "wkst" rule parts MUST be a string as specified in , with case preserved. The value of the "until" rule part MUST be a date or date-time value formatted in accordance to the rules for date or date-time specified in this document. The "count" and "interval" rule parts MUST be specified as a single JSON number value. The following rule parts can have one or more numeric values: "bysecond", "byminute", "byhour", "bymonthday", "byyearday", "byweekno", "bymonth", and "bysetpos". If a rule part contains multiple values, an array of numbers MUST be used for that rule part. Single-valued rule parts can be represented either using a single number value, omitting the array completely, or an array with one number element. A jCal parser MUST be able to understand both data types. Similarly, the "byday" rule part can have one or more string values. If it contains multiple values, an array of strings MUST be used. As before, a single-valued rule part can be represented either using a single string value or an array with one string element, both of which a jCal parser MUST be able to understand.

iCalendar "TEXT" property values are represented by a property with the type identifier "text". The value elements are JSON strings.

iCalendar "TIME" property values are represented by a property with the type identifier "time". The value elements are JSON strings with the same time value specified by , but represented using the extended format of the complete representation specified in , Section 4.2.2.2. Other variations, for example representation with reduced accuracy, MUST NOT be used. The same restrictions with respect to leap seconds, time fractions, and timezone offsets as specified in Section 3.3.12 apply.

iCalendar "URI" property values are represented by a property with the type identifier "uri". The value elements are JSON strings representing the URI.

iCalendar "UTC-OFFSET" property values are represented by a property with the type identifier "utc-offset". The value elements are JSON strings with the same UTC offset value specified by , with the exception that the hour and minute components are separated by a ":" character, for consistency with the timezone offset, extended format.

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 for how to deal with default values for unrecognized extension properties or property parameters.

Converting jCal to iCalendar reverses the process described in . This section describes a few additional requirements for conversion. When converting component, property and property parameter names, they 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 . During conversion, JSON escaping MUST be unescaped. Afterwards, iCalendar escaping, as defined by and MUST be applied. Finally, long lines SHOULD be folded as described in , Section 3.1. Non-binary value types MUST NOT be base64 encoded. When converting to iCalendar, the VALUE parameter MUST be added to properties whose default value type is unknown, but do not have a jCal type identifier "unknown". The VALUE parameter MAY be omitted for properties using the default value type. The VALUE parameter MUST be omitted for properties which have the jCal type identifier "unknown".

In iCalendar, properties can have one or more value types as specified by their definition, with one of those values being defined as the default. When a property uses its default value type, the "VALUE" property parameter does not need to be specified on the property. For example, "DTSTART"'s default value type is "DATE-TIME", so "VALUE=DATE-TIME" need not be set as a property parameter. However, "DTSTART" also allows a "DATE" value to be specified, and if that is used, "VALUE=DATE" has to be set as a property parameter. 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. In jCal, a new "unknown" property value type is introduced. Its purpose is to allow preserving unknown property values when round-tripping between jCal and iCalendar. To avoid collisions, this specification reserves the UNKNOWN property value type in iCalendar. It MUST NOT be used in any iCalendar as specified by , nor any extensions to it. The type is hence registered to the iCalendar Value Data Types registry in .

Any property that does not include a "VALUE" property parameter and whose default value type is not known, MUST be converted to a primitive JSON string. The content of that string is the unprocessed value text. Also, value type MUST be set to "unknown". To correctly implement this format, it is critical that if the default type is not known that the type "unknown" is used. If this requirement is ignored and for example "text" is used, additional escaping may occur which breaks round-tripping values. Any unrecognized property parameter MUST be converted to a string value, with its content set to the property parameter value text, treated as if it were a "TEXT" value.

In jCal the value type is always explicitly specified. It is converted to iCalendar using the iCalendar VALUE parameter, except in the following two cases: If the value type specified in jCal matches the default value type in iCalendar, the VALUE parameter MAY be omitted. If the value type specified in jCal is set to "unknown", the VALUE parameter MUST NOT be specified. The value MUST be taken over in iCalendar without processing.

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:

jCal:

The following is an example of how to cope with jCal data where the parser was unable to identify the type. Note how the "unknown" value type is not added to the iCalendar data and escaping, aside from standard JSON string escaping, is not processed.

jCal:

iCalendar:

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:

iCalendar:

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:

jCal:

This specification defines how iCalendar data can be "translated" between two different data formats - the original text format and JSON - with a one-to-one mapping to ensure all the semantic data in one format (properties, parameters and values) are preserved in the other. It does not change the semantic meaning of the underlying data itself, or impose or remove any security considerations that apply to the underlying data. The use of JSON as a format does have its own inherent security risks as discussed in Section 12 of . Even though JSON is considered a safe subset of JavaScript, it should be kept in mind that a flaw in the parser processing JSON could still impose a threat which doesn't arise with conventional iCalendar data. With this in mind, a parser for JSON data should be used for jCal that is aware of the security implications. For example, the use of JavaScript's eval() function is considered an unacceptable security risk, as described in , Section 12. A native parser with full awareness of the JSON format should be preferred. In addition, it is expected that this new format will result in iCalendar data being more widely disseminated (e.g., with use in web applications rather than just dedicated calendaring applications). In all cases, application developers have to conform to the semantics of the iCalendar data as defined by and associated extensions, and all of the security considerations described in Section 7 of , or any associated extensions, are applicable.

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. application calendar+json none "method", "component" and "optinfo" as defined for the text/calendar media type in , Section 8.1. Same as encoding considerations of application/json as specified in , Section 11. See . This media type provides an alternative format for iCalendar data based on JSON. This specification. Applications that currently make use of the text/calendar media type can use this as an alternative. Similarly, Applications that use the application/json media type to transfer calendaring data can use this to further specify the content. N/A N/A N/A N/A N/A calsify@ietf.org COMMON There are no restrictions on where this media type can be used. See the "Author's Address" section of this document. IETF

IANA is asked to add the following entry to the iCalendar Data Types registry: UNKNOWN To allow preserving property values whose default value type is not known during round-tripping between jCal and iCalendar. (Not applicable) The UNKNOWN value data type is reserved for the exclusive use of the jCal format. Its use is described in of this document. As this registration serves as a reservation of the UNKNOWN type so that it is not used in iCalendar, there is no applicable iCalendar example. Examples of its usage in jCal can be found in this document. IANA is asked to make the "Status" column for this entry in the registry say, "Reserved - Do not use" and to make the "Reference" column refer to of this document.

The authors would like to thank the following for their valuable contributions: William Gill, Erwin Rehme, and Dave Thewlis, Simon Perreault, Michael Angstadt, Peter Saint-Andre, Bert Greevenbosch, Javier Godoy. This specification originated from the work of the XML-JSON technical committee of the Calendaring and Scheduling Consortium.

&rfc2119; &rfc5234; &rfc4648; &rfc5545; &rfc6321; &rfc3986; &rfc6868; &rfc7159; International Organization for Standardization &rfc6982; The Calendaring and Scheduling Consortium

This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in . The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to , "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit". ICAL.js - Philipp Kewisch, James Lal. A JavaScript parser for iCalendar (rfc5545) https://github.com/mozilla-comm/ical.js/ production All aspects of this draft, up to version 01. Includes an online validator. (as of rev 847c67c501, 2013-02-14) MPL, Mozilla Public License 2.0 Py Calendar - Cyrus Daboo. iCalendar/vCard Library https://svn.calendarserver.org/repository/calendarserver/PyCalendar/branches/json/ production All aspects of this draft, up to version 01. Apache License, Version 2.0 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.

Below is an ABNF schema as per for iCalendar in JSON. ABNF Symbols not described here are taken from . The schema is non-normative and given for reference only. The numeric section numbers given in the comments refer to section in . 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 . Additional schemas may be available on the internet at .

This section contains two examples of iCalendar objects with their jCal representation.

Added information on how to handle multi-value parameter. The decision leads to a cleaner draft for a similar proposal for vcard. Removed the open discussion point section regarding the mime media type in favor of adding one. Minor corrections in wording and typo fixes. Added implementation status section. Removed various text tables that just show a conversion from uppercase to lowercase. Changed value format for RECUR and PERIOD types Minor corrections in wording and typo fixes. Publication as a WG draft Changed handling of GEO and REQUEST-STATUS to align with jCard Corrections and additions to the ABNF Section Added a further sentence on preprocessing and escaping to clarify that JSON escaping must be used. Changed handling of unknown property parameter types. Minor corrections and fixing typos. Changed wording around RECUR value handling. Minor corrections and fixing typos. Changed wording around RECUR value handling again. Added reference to rfc6868 for both directions Resolved a few MAY/SHOULD conflicts Improved UNKNOWN registration by only putting iCalendar related information into the registration template. Removed the stream construct, replaced with general information on how to handle iCalendar streams. Corrected some examples and ABNF Corrected trailing commas in some examples. Corrected rrule examples to use object syntax. Corrected "request-status" example to use an array. Updated UNKNOWN registration text as per iCalendar expert suggestion. Minor fix in an example. Editorial changes for alignment with draft-ietf-jcardcal-jcard. Editorial changes in preparation for IETF last call. Removed reference to jcard draft Made more clear that parsers MUST be able to understand both single-valued and array data types. Updated references from rfc4627 to rfc7159 Added a paragraph on number formats between iCalendar and JSON Additions and corrections to conversion from jCal to iCalendar and moved redundant paragraph from Section 3.1 to 4. Addded references to ISO.8501.2004 for ABNF of date/time rules. Fixed typos in informative ABNF