Responses for Activity Streams (Draft)
json-activity-01

Abstract

This specification details an extension to the JSON Activity Streams to express the serialization of responses and reactions to an Activity or an Object.

Status of this Memo

This document is an Internet-Draft and is NOT offered in accordance with Section 10 of RFC 2026, and the author does not provide the IETF with any rights other than to publish as an Internet-Draft.

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This Internet-Draft will expire on October 3, 2011.

Table of Contents

1.  Introduction
2.  Notational Conventions
3.  The "inReplyTo" Property
4.  Responses and Activity Summaries
5.  Security Considerations
6.  Normative References
Appendix A.  Acknowledgements
§  Author's Address

1.  Introduction

The Activity Streams specification defines a format for describing socially interesting events, or "Activities", about the people and things an individual may care about. This specification describes the mechanisms by which responses or reactions to those events or their related objects may also be described.

The possible range of reactions to an event or object vary broadly and include such actions as posting a comment, sharing the event with others, "liking" or "favoriting" the event or object, RSVP'ing to an event invite and so on. This specification does not attempt to cover the full range of possible reactions. Rather, it seeks to establish a common pattern for the expression of those reactions within an Activity Stream and defines a set of extension properties exemplifying that pattern.

2.  Notational Conventions

The text of this specification provides the sole definition of conformance. Examples in this specification are non-normative.

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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  The "inReplyTo" Property

The inReplyTo property MAY be used within any Activity Stream object to identify other objects for which the containing object is considered a response. The value of the inReplyTo property is a JSON (Crockford, D., “The application/json Media Type for JavaScript Object Notation (JSON),” July 2006.) [RFC4627] Array of Activity Stream Objects. For example:

 
  {
    "objectType": "comment",
    "content": "<p>This is a comment</p>",
    "inReplyTo": [
      {
        "objectType": "note",
        "id": "http://example.org/objects/123",
        "displayName": "A simple note"
      }
    ]
  }

In many cases, such as when an object appears as a member of a collection of objects in a property that clearly indicates a response or reaction relationship with a parent object, the inReplyTo property can be implied. For instance, the replies property defined below in Section 4 (Responses and Activity Summaries) may contain a listing of child objects with an implied inReplyTo property referring to the parent object.

4.  Responses and Activity Summaries

It is common practice to provide summary information on the number and types of activities that have occurred with respect to a given object. For instance, a "note" object may have been the target of any number of comment, like, or share activities. This summary information MAY be expressed in the JSON serialization of an object by using a property name descriptive of the data being summarized and using the Collection object as defined by the JSON Activity Streams document.

The following properties MAY be used on any object type or activity for each of the specified situations:

The following example illustrates the use of these properties. Note that the value of the totalItems property indicates the total number of items in the associated collections and may not match the actual number of objects in the items property. For instance, in the example below, for the likes property, the totalItems property specifies the value 120 but includes only a single object. This SHOULD be interpreted along the lines of "John and 119 other users like this note".

 
  {
    "objectType": "note",
    "displayName": "A Simple Note",
    "content": "<p>This is a simple note</p>",
    "replies": {
      "totalItems": 10,
      "url": "http://example.org/comments-stream",
    },
    "followers": {
      "totalItems": 15,
      "url": "http://example.org/followers-stream",
      "items": [
        {
          "objectType": "person",
          "displayName": "Jane"
        }
      ]
    },
    "likes": {
      "totalItems": 120,
      "items": [
        "objectType": "person",
        "displayName": "John"
      ]
    },
    "reviews": {
      "totalItems": 1,
      "items": [
        {
          "objectType": "review",
          "author": {
            "displayName": "Joe",
            "objectType": "person"
          },
          "rating": 4.5
        }
      ]
    }
  }

5.  Security Considerations

The mechanisms defined herein are subject to the same security considerations as all activities. Applications must be aware of the risk posed by a malicious third party attempting to artificially inject inappropriate content into the stream of responses and replies of an object. For instance, services that aggregate activity streams from multiple sources and attempt to reconstruct a thread of discussion using replies and response from across those sources could be tricked into displaying illegitimate content if appropriate consideration is not given to the content origin. Mitigation of such threats is considered out of scope for this specification.

6. Normative References

Appendix A.  Acknowledgements

...

Author's Address