Activity Streams

Please check the errata for any errors or issues reported since publication. The English version of this specification is the only normative version. Non-normative translations may also be available. This specification details a model for representing potential and completed activities using the JSON format. It is intended to be used with vocabularies that detail the structure of activities, and define specific types of activities. This draft is heavily influenced by the JSON Activity Streams 1.0 specification originally co-authored by Martin Atkins, Will Norris, Chris Messina, Monica Wilkinson, Rob Dolin and James Snell. The author is very thankful for their significant contributions and gladly stands on their shoulders. Some portions of the original text of Activity Streams 1.0 are used in this document. This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at This document was produced by a group operating under the 5 February 2004 W3C Patent Policy . W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy . The JSON Activity Streams 1.0 [AS1 ] specification was published in May of 2011 and provided a baseline extensible syntax for the expression of completed activities. This specification builds upon that initial foundation by incorporating lessons learned through extensive implementation, community feedback and related ongoing work from a variety of other communities. Some of the issues that specifically motivated the evolution of Activity Streams 2.0 from Activity Streams 1.0 include: This specification describes a JSON-based [RFC7159 ] serialization syntax for the Activity Vocabulary that conforms to a subset of [JSON-LD ] syntax constraints but does not require JSON-LD processing. While other serialization forms are possible, such alternatives are not discussed by this document. Activity Streams 2.0 documents MUST be serialized using the UTF-8 character encoding. The serialized JSON form of an Activity Streams 2.0 document MUST be consistent with what would be produced by the standard JSON-LD 1.0 Processing Algorithms and API [JSON-LD-API ] Compaction Algorithm using, at least, the normative JSON-LD @context definition provided here . Implementations MAY augment the provided @context with additional @context definitions but MUST NOT override or change the normative context. Implementations MAY also use additional properties and values not defined in the JSON-LD @context with the understanding that any such properties will likely be unsupported and ignored by consuming implementations that use the standard JSON-LD algorithms. See the Extensibility section for more information on handling extensions within Activity Streams 2.0 documents. JSON-LD uses the special @context property to define the processing context . The value of the @context property is defined by the [JSON-LD ] specification. Implementations producing Activity Streams 2.0 documents SHOULD include a @context property with a value that includes a reference to the normative Activity Streams 2.0 JSON-LD @context definition using the URL " Implementations MAY use the alternative URL " instead. This can be done using a string, object, or array. Figure 2 Document providing context as an object using the @vocab keyword and a prefix for extension terms. When a JSON-LD enabled Activity Streams 2.0 implementation encounters a JSON document identified using the " application/activity+json " MIME media type, and that document does not contain a @conte