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Activity Streams (http://activitystrea.ms)                      J. Snell
Internet-Draft                                                       IBM
Intended status: Standards Track                                M. Marum
Expires: November 2, 2014                                       SugarCRM
                                                             May 1, 2014


              JSON Activity Streams 2.0 - Action Handlers
                 draft-snell-activitystreams-actions-04

Abstract

   This specification defines Action Handlers for use with the Activity
   Streams 2.0 format.

Author's Note

   Note that this document is a work-in-progress draft specification
   that does not yet represent a "standard".  It is the intention of
   this specification to propose a few new ideas and openly solicit
   feedback on their definition and use.  While this document might
   eventually evolve into an RFC the ideas described herein have not yet
   been broadly implemented and have definitions that will evolve
   through successive iterations of this draft.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 2, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Action Handlers . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  HTTP Action Handler . . . . . . . . . . . . . . . . . . . . .   6
   4.  Embed Action Handler  . . . . . . . . . . . . . . . . . . . .  10
   5.  Intent Action Handler . . . . . . . . . . . . . . . . . . . .  13
   6.  Using "service" and "application" objects as action handlers   13
   7.  HTML Form Objects . . . . . . . . . . . . . . . . . . . . . .  14
   8.  Typed Payload Objects . . . . . . . . . . . . . . . . . . . .  15
   9.  URL Template Objects  . . . . . . . . . . . . . . . . . . . .  16
   10. Parameters Object . . . . . . . . . . . . . . . . . . . . . .  17
     10.1.  The Parameter Object . . . . . . . . . . . . . . . . . .  18
     10.2.  Using UrlTemplate and TypedPayload objects as parameter
            descriptions . . . . . . . . . . . . . . . . . . . . . .  22
   11. Authentication Object . . . . . . . . . . . . . . . . . . . .  23
   12. Styles Object . . . . . . . . . . . . . . . . . . . . . . . .  24
   13. Security Considerations . . . . . . . . . . . . . . . . . . .  26
   14. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   15. Normative References  . . . . . . . . . . . . . . . . . . . .  26
   Appendix A.  Using Action Handlers From Other Vocabularies  . . .  26
     A.1.  Schema.org Actions Proposal . . . . . . . . . . . . . . .  26
     A.2.  Google's "Actions in the Inbox" . . . . . . . . . . . . .  27
     A.3.  Mixing Vocabularies . . . . . . . . . . . . . . . . . . .  28
     A.4.  Example Drawing From Multiple Vocabularies  . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Overview

   The Activity Streams 2.0 [I-D.snell-activitystreams] specification
   introduces the notion of "actions" that can be associated with
   objects.  Using the "actions" property described in Sections 3.6 and
   3.6.1 of the Activity Streams 2.0 document, the producer of an object
   can declare a specific set of verbs appropriate for the object and
   map each of those to one or more objects ("action handlers") or
   resources capable of "carrying out" the verb.  This document expands
   on that mechanism by defining and describing a core set of action
   handler object types.



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2.  Action Handlers

   An action handler is an Activity Streams 2.0 object whose objectType
   and member properties instruct a consuming application how to carry
   out the verb the action handler has been associated with.  For
   instance, given the following example:

     {
       "objectType": "note",
       "displayName": "Title of the note",
       "content": "This is a simple note.",
       "actions": {
         "share": {
           "objectType": "HttpActionHandler",
           "url": "http://example.org/share"
         },
         "like": {
           "objectType": "EmbedActionHandler",
           "mediaType": "text/plain",
           "content": "Hello World"
         }
       }
     }

   The "note" object has two declared actions, "share" and "like".  Each
   of those is associated with one action handler object.  The "share"
   action has a action handler of type "HttpActionHandler", while the
   "like" action has an "EmbedActionHandler".

   As illustrated in the example, action handlers are represented as
   Activity Streams 2.0 objects.  All such objects share a common set of
   base member properties as defined in the following table:

   +----------+-----------------------------+--------------------------+
   | Property | Value                       | Description              |
   +----------+-----------------------------+--------------------------+
   | confirm  | Boolean                     | True if the consuming    |
   |          |                             | application ought to     |
   |          |                             | seek confirmation prior  |
   |          |                             | to using the action      |
   |          |                             | handler to carry out     |
   |          |                             | it's associated action.  |
   |          |                             | Defaults to False.       |
   | context  | JSON Object                 | Contextual information   |
   |          |                             | associated with the      |
   |          |                             | action handler,          |
   |          |                             | represented as a JSON    |
   |          |                             | Object without any       |



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   |          |                             | particular structure.    |
   |          |                             | How the context is used  |
   |          |                             | is dependent entirely on |
   |          |                             | the action handler       |
   |          |                             | definition and on how a  |
   |          |                             | consuming application    |
   |          |                             | chooses to implement the |
   |          |                             | action handler.          |
   | expects  | Link Value                  | For action handlers with |
   |          | [I-D.snell-activitystreams] | a distinct input         |
   |          |                             | requirement (e.g.        |
   |          |                             | HttpActionHandler), the  |
   |          |                             | expects property         |
   |          |                             | provides a description   |
   |          |                             | of the expected input.   |
   |          |                             | The value is expressed   |
   |          |                             | as either a String       |
   |          |                             | containing a fully       |
   |          |                             | qualified IRI, an        |
   |          |                             | Activity Stream Object,  |
   |          |                             | or an Array of IRI's or  |
   |          |                             | Objects.  When multiple  |
   |          |                             | values are provided,     |
   |          |                             | they MUST be considered  |
   |          |                             | as mutually exclusive    |
   |          |                             | alternatives.            |
   | returns  | Link Value                  | For action handlers with |
   |          | [I-D.snell-activitystreams] | a distinct output, the   |
   |          |                             | returns property         |
   |          |                             | provides a description   |
   |          |                             | of the expected output.  |
   |          |                             | The value is expressed   |
   |          |                             | as either a String       |
   |          |                             | containing a fully       |
   |          |                             | qualified IRI, an        |
   |          |                             | Activity Stream Object,  |
   |          |                             | or an Array of IRI's or  |
   |          |                             | Objects. When multiple   |
   |          |                             | values are provided,     |
   |          |                             | they MUST be considered  |
   |          |                             | as mutually exclusive    |
   |          |                             | alternatives.            |
   | auth     | Authentication Value        | For action handlers with |
   |          | (Section 11)                | specific authentication  |
   |          |                             | requirements, the "auth" |
   |          |                             | property provides        |
   |          |                             | information about the    |
   |          |                             | specific authentication  |



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   |          |                             | mechanisms supported.    |
   | requires | Link Value                  | An optional Link Value   |
   |          | [I-D.snell-activitystreams] | whose value(s) describe  |
   |          |                             | features or behaviors an |
   |          |                             | implementation MUST      |
   |          |                             | support in order to      |
   |          |                             | carry out the action.    |
   |          |                             | Requirements are         |
   |          |                             | designed to be           |
   |          |                             | intentionally open-ended |
   |          |                             | and will vary depending  |
   |          |                             | on specific Action       |
   |          |                             | Handler type. Any        |
   |          |                             | implementation that does |
   |          |                             | not support any          |
   |          |                             | specified required       |
   |          |                             | feature MUST ignore the  |
   |          |                             | Action Handler.          |
   | prefers  | Link Value                  | An optional Link Value   |
   |          | [I-D.snell-activitystreams] | whose value(s) describe  |
   |          |                             | features or behaviors an |
   |          |                             | implementation SHOULD    |
   |          |                             | support in order to      |
   |          |                             | carry out the action.    |
   |          |                             | Requirements are         |
   |          |                             | designed to be           |
   |          |                             | intentionally open-ended |
   |          |                             | and will vary depending  |
   |          |                             | on specific Action       |
   |          |                             | Handler type. Any        |
   |          |                             | implementation that does |
   |          |                             | not support any          |
   |          |                             | specified preferred      |
   |          |                             | feature MAY ignore the   |
   |          |                             | feature.                 |
   +----------+-----------------------------+--------------------------+

   This specification defines three specific base types of action
   handler:

   o  The HTTP Action Handler (Section 3),

   o  The Embed Action Handler (Section 4), and

   o  The Intent Action Handler (Section 5).

   Implementations are free to use Activity Stream objects of any
   objectType as an action handler.  Consuming applications MAY ignore



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   any object it encounters that use objectTypes that are not recognized
   or supported as action handlers.  Alternatively, the consuming
   application MAY treat such objects as implied Intent Action Handlers
   (Section 5).

   Multiple independent action handlers can be associated with any
   single verb using a JSON Array.  The ordering of objects within such
   an array is not considered to be significant.

   For example, in the following, the "share" action has two associated
   action handlers:

     {
       "objectType": "event",
       "displayName": "Party!",
       "content": "We're going to party like it's 1999!",
       "id": "urn:example:events:123",
       "actions": {
         "share": [
           {
             "objectType": "HttpActionHandler",
             "method": "POST",
             "url": "http://example.org/share-this/123",
             "target": "DIALOG",
             "returns": {
               "objectType": "TypedPayload",
               "mediaType": "text/html"
             }
           },
           {
             "objectType": "EmbedActionHandler",
             "mediaType": "text/html",
             "content": "<div>...</div>"
           }
         ]
       }
     }

3.  HTTP Action Handler

   An HTTP Action Handler describes an HTTP request/response flow that
   is used to carry out an action.  It is identified using an objectType
   value of "HttpActionHandler".








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   +----------+-----------------------------------+--------------------+
   | Property | Value                             | Description        |
   +----------+-----------------------------------+--------------------+
   | url      | Link Value                        | Specifies the HTTP |
   |          |                                   | or HTTPS URL to    |
   |          |                                   | which the HTTP     |
   |          |                                   | request is         |
   |          |                                   | directed.          |
   | method   | HTTP Method String (e.g. "GET",   | The HTTP method to |
   |          | "POST", "PUT", etc)               | use. Defaults to   |
   |          |                                   | "GET"              |
   | target   | "DEFAULT" - Consumer defined      | Specifies the      |
   |          | default; "NONE" - No navigation   | intended target of |
   |          | or UI context (e.g. a hidden HTTP | the HTTP action.   |
   |          | action that does not result in    | This determines    |
   |          | the creation or use of a browser  | whether the action |
   |          | window); "NEW" - A new navigation | results in a new   |
   |          | or UI context (e.g. show the      | navigation context |
   |          | results of the HTTP request in a  | (e.g. new browser  |
   |          | browser window or tab.);          | window) or whether |
   |          | "CURRENT" - Reuse the existing    | the action is      |
   |          | navigation or UI context (e.g.    | "hidden". When not |
   |          | show the results of the HTTP      | specified,         |
   |          | request in an existing browser    | defaults to        |
   |          | window or tab.); {Other token     | "DEFAULT", meaning |
   |          | value} - Any other TOKEN value.   | that the consuming |
   |          | Interpretation and support of     | application is     |
   |          | such extension tokens is          | free to determine  |
   |          | dependent on the consuming        | an appropriate     |
   |          | application. Unknown or           | target context.    |
   |          | unsupported values MUST be        |                    |
   |          | ignored.                          |                    |
   +----------+-----------------------------------+--------------------+

   For example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": {
           "objectType": "HttpActionHandler",
           "url": "http://example.org/foo",
           "method": "GET"
         }
       }
     }



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   As a shortcut, HttpActionHandlers that use the "GET" method and a
   "DEFAULT" target can be specified using a JSON string containing the
   absolute URL.  For instance:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": "http://example.org/foo"
       }
     }

   In the Activity Streams 2.0 format, the "url" property is defined as
   a "Link Value", this means that it is possible for the value of the
   "url" property to be an Activity Stream object that a consuming
   application can use to resolve the actual target URL.  This
   specification defines a new UrlTemplate (Section 9) objectType
   specifically intended for such use.

   The UrlTemplate object can be used within an HTTP Action Handler, for
   instance, whenever carrying out the HTTP request requires the
   construction of a new URL that includes variable parameters:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "review": {
           "objectType": "HttpActionHandler",
           "url": {
             "objectType": "UrlTemplate",
             "template": "http://example.org/note/123{?rating}",
             "parameters": {
               "rating": {
                 "displayName": "Rating",
                 "maxInclusive": 5,
                 "minInclusive": 1,
                 "type": "unsignedInt"
               }
             }
           },
           "method": "POST",
           "target": "NEW"
         }
       }
     }



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   If the intended HTTP request uses the GET method and DEFAULT target,
   the UrlTemplate object itself can be used directly as the action
   handler.

   "GET" HttpActionHandler shortcut using a URL Template:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": {
           "objectType": "UrlTemplate",
           "template": "http://example.org/note/{noteid}",
           "parameters": {
             "noteid": {
               "type": "nonNegativeInteger",
               "totalDigits": 5
             }
           }
         }
       }
     }

   If the HTTP request requires an input payload, the HttpActionHandler
   object can contain an "expects" property.  The value of "expects" is
   an Activity Streams 2.0 "Link Value" represented either as a simple
   JSON string containing a fully qualified IRI, an Activity Stream
   object, or an array of IRI's or Objects.  This specification defines
   a new HtmlForm (Section 7) objectType to be used whenever the input
   of the HTTP request is an HTML Form POST.  A new TypedPayload
   (Section 8) objectType is defined for use whenever the input is an
   arbitrary MIME media type.

   For example, the following describes an HTML Form post with a single
   "foo" parameter submitted using the "application/x-www-form-
   urlencoded" format:














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     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "share": {
           "objectType": "HttpActionHandler",
           "method": "POST",
           "url": "http://example.org/foo",
           "expects": {
             "objectType": "HtmlForm",
             "mediaType": "application/x-www-form-urlencoded",
             "parameters": {
               "foo": {
                 "type": "string",
                 "displayName": "Foo Property"
               }
             }
           }
         }
       }
     }

4.  Embed Action Handler

   An Embed Action Handler defines static or dynamic content to be
   visually rendered to carry out an action.  Examples of embeds can
   include static HTML, images, videos, gadgets and applications.  It is
   identified using an objectType value of "EmbedActionHandler".






















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   +-------------+------------------------+----------------------------+
   | Property    | Value                  | Description                |
   +-------------+------------------------+----------------------------+
   | url         | Link Value             | Yes if "content" is not    |
   |             |                        | specified.                 |
   | The URL     | content                | String                     |
   | from which  |                        |                            |
   | to retrieve |                        |                            |
   | the content |                        |                            |
   | for this    |                        |                            |
   | embed.      |                        |                            |
   | Yes if      | The character based    | mediaType                  |
   | "url" is    | "static" content to be |                            |
   | not         | embeded. The           |                            |
   | specified.  | "mediaType" parameter  |                            |
   |             | specifies the MIME     |                            |
   |             | media type of the      |                            |
   |             | content.               |                            |
   | MIME Media  | No (but strongly       | The MIME Media Type of the |
   | Type        | recommended)           | embedded content.          |
   | style       | Styles Object (Section | Visual CSS styling hints   |
   |             | 12)                    | to apply to the element    |
   |             |                        | containing the embedded    |
   |             |                        | content.                   |
   | preview     | Link Value             | A reference to a "preview" |
   |             |                        | representation of the      |
   |             |                        | embedded content.          |
   |             |                        | Typically, this would a    |
   |             |                        | URL to a thumbnail or      |
   |             |                        | screenshot image of the    |
   |             |                        | content.                   |
   | target      | "DEFAULT"; "INLINE";   |                            |
   |             | {Other token value}    |                            |
   +-------------+------------------------+----------------------------+

   In the following example, the "view" action is associated with an
   "EmbedActionHandler" containing a static fragment of HTML markup:














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     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": {
           "objectType": "EmbedActionHandler",
           "content": "<div>This is some bit of embedded HTML</div>",
           "mediaType": "text/html",
           "style": {
             "height": "100px",
             "width": "100px",
             "box-shadow": "10px 10px 5px #888888"
           },
           "displayName": "Some embedded content",
           "preview": "http://example.org/preview/123.jpg"
         }
       }
     }

   Alternatively, the embedded content can be referenced by URL:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": {
           "objectType": "EmbedActionHandler",
           "url": "http://example.org/foo",
           "mediaType": "text/html"
         }
       }
     }

   The mediaType parameter specifies the type of content to be embedded.
   Consuming applications MAY ignore Embed Action Handlers that specify
   unrecognized or unsupported mediaTypes.













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   Example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "view": {
           "objectType": "EmbedActionHandler",
           "url": "http://example.org/foo.mpg",
           "mediaType": "video/mpeg"
         }
       }
     }

5.  Intent Action Handler

   An Intent Action Handler provides a generic way for the publisher of
   an Activity object to tell the consuming application to figure out
   how to handle the action on it's own.  The consumer can, for
   instance, pass the object off to some other native platform
   application.  It is identified using an objectType value of
   "IntentActionHandler".

   For example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "share": {
           "objectType": "IntentActionHandler",
           "displayName": "Share This",
           "context": {
             "foo": "ABC",
             "bar": 123
           }
         }
       }
     }

6.  Using "service" and "application" objects as action handlers

   The "service" and "application" object are existing objectTypes
   defined by the Activity Streams 1.0 core schema.  While these objects
   were not originally designed to be used as action handlers, they can
   be.  Specifically, the "service" objectType can be used when the



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   action is to be carried out using some specific third party service
   interface; the "application" objectType can be used when the action
   is to be carried out by deferring some some specific native platform
   application.

   For example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "share": {
           "objectType": "service",
           "displayName": "My Sharing Service",
           "url": "http://share.example.org/api"
         },
         "save": {
           "objectType": "application",
           "displayName": "Read this later!",
           "platform": "android",
           "id": "123",
           "url": "http://play.google.com/..."
         }
       }
     }

7.  HTML Form Objects

   +------------+----------------+-------------------------------------+
   | Property   | Value          | Description                         |
   +------------+----------------+-------------------------------------+
   | mediaType  | MIME Media     | Defaults to "application/x-www-     |
   |            | Type           | form-urlencoded"                    |
   | parameters | Parameters     | Defines the HTML form parameters.   |
   |            | Object         |                                     |
   |            | (Section 10)   |                                     |
   +------------+----------------+-------------------------------------+













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   For example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "review": {
           "objectType": "HttpActionHandler",
           "method": "POST",
           "url": "http://example.org/foo",
           "expects": {
             "objectType": "HtmlForm",
             "mediaType": "application/x-www-form-urlencoded",
             "parameters": {
               "foo": {
                 "displayName": "Foo",
                 "type": "string",
                 "placeholder": "Foo"
               },
               "bar": {
                 "type": "string",
                 "value": "Provided Value"
               }
             }
           }
         }
       }
     }

   Is roughly equivalent to the following HTML form:

     <form method="post" action="http://example.org/foo">
       <label for="foo">Foo:</label>
       <input id="foo" name="foo" type="input" placeholder="Foo" />
       <input name="bar" type="hidden" value="Provided Value" />
       <input type="submit" />
     </form>

8.  Typed Payload Objects











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   +-----------+-----------------------------+-------------------------+
   | Property  | Value                       | Description             |
   +-----------+-----------------------------+-------------------------+
   | mediaType | MIME Media Type             | The MIME Media Type of  |
   |           |                             | the Payload             |
   | type      | Type Value                  | An optional Type Value  |
   |           | [I-D.snell-activitystreams] | that describes the      |
   |           |                             | payloads semantic type. |
   | schema    | Link Value                  | An optional Link Value  |
   |           | [I-D.snell-activitystreams] | whose value(s) describe |
   |           |                             | the structure of the    |
   |           |                             | payload data. The value |
   |           |                             | is represented either   |
   |           |                             | as a String with a      |
   |           |                             | fully qualified IRI, an |
   |           |                             | Activity Stream object, |
   |           |                             | or an Array of IRIs and |
   |           |                             | Objects. If multiple    |
   |           |                             | values are provided,    |
   |           |                             | they are to be          |
   |           |                             | considered mutually     |
   |           |                             | exclusive alternatives. |
   +-----------+-----------------------------+-------------------------+

   For example:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "review": {
           "objectType": "HttpActionHandler",
           "method": "POST",
           "url": "http://example.org/foo",
           "expects": {
             "objectType": "TypedPayload",
             "mediaType": "text/json",
           }
         }
       }
     }

9.  URL Template Objects

   Objects with the "UrlTemplate" object type represent [RFC6570] URL
   Templates.




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   +------------+-------------------------+----------------------------+
   | Property   | Value                   | Description                |
   +------------+-------------------------+----------------------------+
   | template   | URL Template            | The [RFC6570] URL Template |
   | parameters | Parameters Object       | Defines the URL Template   |
   |            | (Section 10)            | parameters                 |
   +------------+-------------------------+----------------------------+

   {
     "objectType": "note",
     "displayName": "A simple note object",
     "content": "This is a simple note.",
     "actions": {
       "review": {
         "objectType": "UrlTemplate",
         "template": "http://example.org/notes/{noteid}",
         "parameters": {
           "noteid": {
             "type": "nonNegativeInteger",
             "totalDigits": 5
           }
         }
       }
     }
   }

   If the given URL template includes any parameter tokens that do not
   appear within the "parameters" property, the parameter value type is
   assumed to be a UTF-8 encoded xsd:string with no maximum length.

10.  Parameters Object

   A Parameters Object is used to provide descriptions of the variable
   inputs of objects such as HTML Forms (Section 7) and URL Templates
   (Section 9).  The object is expressed as a JSON dictionary mapping
   parameter names to parameter descriptions which take the form of
   either an XML Schema type name [W3C.REC-xmlschema-2-20041028], an
   absolute IRI, a parameter object (Section 10.1), or in some limited
   cases, TypedPayload or UrlTemplate objects.

   By default, all parameters are assumed to be required.  When a
   parameter is described using an object, the object MAY contain a
   boolean "required" member.  If "required" is false, use of the
   parameter is assumed to be optional.







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   Using the Parameters Object in UrlTemplate objects:

     {
       "objectType": "UrlTemplate",
       "template": "http://example.org{/foo,bar}"
       "parameters": {
         "foo": "string",
         "bar": {
           "type": "string",
           "required": false
         }
       }
     }

   In this example, both the "foo" and "bar" parameter conform to the
   XML Schema type "xsd:string".  The "foo" parameter is required while
   the "bar" parameter is optional.

   Using the Parameters Object in HtmlForm objects:

     {
       "objectType": "HtmlForm",
       "mediaType": "application/x-www-form-urlencoded",
       "parameters": {
         "foo": {
           "displayName": "Foo",
           "type": "string"
         },
         "bar": {
           "displayName": "Bar",
           "type": "string",
           "required": false
         }
       }
     }

10.1.  The Parameter Object

   Parameter objects provide a rich description of a single parameter in
   a manner that is aligned with the commonly used XML Schema type
   system [W3C.REC-xmlschema-2-20041028].

   +-------------+--------------------------+--------------------------+
   | Property    | Value                    | Description              |
   +-------------+--------------------------+--------------------------+
   | displayName | Natural Language Value [ | An Activity Streams 2.0  |
   |             | I-D.snell-activitystream | Natural Language Value.  |
   |             | s]                       |                          |



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   | required    | boolean                  | True if the parameter is |
   |             |                          | required. Defaults to    |
   |             |                          | true.                    |
   | repeated    | boolean                  | True if the parameter    |
   |             |                          | can be repeated zero or  |
   |             |                          | more times. Defaults to  |
   |             |                          | false.                   |
   | value       | (Any)                    | Provides a fixed value   |
   |             |                          | for the parameter. When  |
   |             |                          | specified,               |
   |             |                          | implementations MUST use |
   |             |                          | the specified value.     |
   | default     | (Any)                    | Provides a default value |
   |             |                          | for the parameter. When  |
   |             |                          | specified,               |
   |             |                          | implementations MUST use |
   |             |                          | the specified value if   |
   |             |                          | no other value is not    |
   |             |                          | supplied.                |
   | type        | XSD [W3C.REC-xmlschema-2 | Identifies the value     |
   |             | -20041028] type name or  | type using either an XML |
   |             | IRI                      | Schema [W3C.REC-xmlschem |
   |             |                          | a-2-20041028] simple     |
   |             |                          | type name or an absolute |
   |             |                          | IRI. If an               |
   |             |                          | implementation           |
   |             |                          | encounters a type it     |
   |             |                          | does not recognize, the  |
   |             |                          | property MAY be ignored. |
   |             |                          | When not specified, the  |
   |             |                          | value type is assumed to |
   |             |                          | be a UTF-8 encoded       |
   |             |                          | "xsd:string".            |
   | enumeration | Array of (Any)           | Provides a fixed array   |
   |             |                          | of possible values for   |
   |             |                          | the parameter.  When     |
   |             |                          | specified,               |
   |             |                          | implementations MUST use |
   |             |                          | one of the specified     |
   |             |                          | values.                  |
   | minLength   | Non-Negative Integer     | Specifies the minimum    |
   |             |                          | "unit of length" for the |
   |             |                          | value. The "unit of      |
   |             |                          | length" depends entirely |
   |             |                          | on the value type as     |
   |             |                          | specified by the "type"  |
   |             |                          | property. For instance,  |
   |             |                          | For xsd:string, the      |



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   |             |                          | length is determined by  |
   |             |                          | the number of            |
   |             |                          | characters; for          |
   |             |                          | xsd:hexBinary, the       |
   |             |                          | length is determined by  |
   |             |                          | the number of encoded    |
   |             |                          | 8-bit octets.            |
   | maxLength   | Non-Negative Integer     | Specifies the maximum    |
   |             |                          | "unit of length" for the |
   |             |                          | value. The "unit of      |
   |             |                          | length" depends entirely |
   |             |                          | on the value type as     |
   |             |                          | specified by the "type"  |
   |             |                          | property. For instance,  |
   |             |                          | For xsd:string, the      |
   |             |                          | length is determined by  |
   |             |                          | the number of            |
   |             |                          | characters; for          |
   |             |                          | xsd:hexBinary, the       |
   |             |                          | length is determined by  |
   |             |                          | the number of encoded    |
   |             |                          | 8-bit octets.            |
   | maxInclusiv | (Any)                    | A value that is          |
   | e           |                          | considered to be the     |
   |             |                          | inclusive upper bound of |
   |             |                          | a range of possible      |
   |             |                          | values. This would       |
   |             |                          | typically be used only   |
   |             |                          | with numeric parameters. |
   | maxExclusiv | (Any)                    | A value that is          |
   | e           |                          | considered to be the     |
   |             |                          | exclusive upper bound of |
   |             |                          | a range of possible      |
   |             |                          | values. This would       |
   |             |                          | typically be used only   |
   |             |                          | with numeric parameters. |
   | minInclusiv | (Any)                    | A value that is          |
   | e           |                          | considered to be the     |
   |             |                          | inclusive lower bound of |
   |             |                          | a range of possible      |
   |             |                          | values. This would       |
   |             |                          | typically be used only   |
   |             |                          | with numeric parameters. |
   | minExclusiv | (Any)                    | A value that is          |
   | e           |                          | considered to be the     |
   |             |                          | exclusive lower bound of |
   |             |                          | a range of possible      |
   |             |                          | values. This would       |



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   |             |                          | typically be used only   |
   |             |                          | with numeric parameters. |
   | step        | Non-negative Number      | Specifies the legal      |
   |             |                          | numeric interval between |
   |             |                          | acceptable values for    |
   |             |                          | the parameter. The step  |
   |             |                          | value MUST be a number   |
   |             |                          | and MUST conform to the  |
   |             |                          | specified type. For      |
   |             |                          | instance, if type is     |
   |             |                          | "unsignedInt", then      |
   |             |                          | step=2 would indicate    |
   |             |                          | legal values of 0, 2, 4, |
   |             |                          | 6, and so on. The step   |
   |             |                          | property MAY be ignored  |
   |             |                          | if it's value does not   |
   |             |                          | correspond to the        |
   |             |                          | expected type.           |
   | totalDigits | Non-negative integer     | Specifies the maximum    |
   |             |                          | number of digits         |
   |             |                          | (integer and fractional) |
   |             |                          | that can be included in  |
   |             |                          | numeric values. The      |
   |             |                          | totalDigits property     |
   |             |                          | MUST be ignored if the   |
   |             |                          | value type identified by |
   |             |                          | the type property is not |
   |             |                          | a numeric type.          |
   | fractionDig | Non-negative integer     | Specifies the maximum    |
   | its         |                          | number of fractional     |
   |             |                          | digits that can be       |
   |             |                          | included in numeric      |
   |             |                          | values. The              |
   |             |                          | fractionDigits property  |
   |             |                          | MUST be ignored if the   |
   |             |                          | value type identified by |
   |             |                          | the type property is not |
   |             |                          | a numeric type.          |
   | pattern     | String or Array of       | One or more Regular      |
   |             | Strings                  | Expressions that         |
   |             |                          | describe the acceptable  |
   |             |                          | structure of the value.  |
   |             |                          | Typically used when the  |
   |             |                          | value is a string.       |
   |             |                          | Multiple patterns are    |
   |             |                          | mutually exclusive       |
   |             |                          | options. That is, the    |
   |             |                          | parameter value is       |



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   |             |                          | expected to conform to   |
   |             |                          | at least one of the      |
   |             |                          | given patterns.          |
   | placeholder | Natural Language Value [ | An optional Natural      |
   |             | I-D.snell-activitystream | Language Value providing |
   |             | s]                       | a text hint that         |
   |             |                          | describes the expected   |
   |             |                          | value of the parameter.  |
   +-------------+--------------------------+--------------------------+

   Using the Parameter Object in HtmlForm objects:

     {
       "objectType": "HtmlForm",
       "mediaType": "application/x-www-form-urlencoded",
       "parameters": {
         "foo": "string",
         "bar": {
           "displayName": "Bar",
           "required": false,
           "repeated": false,
           "type": "unsignedInt",
           "default": 3,
           "minInclusive": 1,
           "maxInclusive": 5
         }
       }
     }

10.2.  Using UrlTemplate and TypedPayload objects as parameter
       descriptions

   In certain cases, when the value of a parameter is expected to be
   either a URI or IRI, the UrlTemplate objectType (Section 9) MAY be
   used as the parameter description.  In such cases, the "required",
   "repeated", "default" and "placeholder" properties from the Parameter
   objectType (Section 10.1) can be used as additional properties within
   the UrlTemplate object.

   For example:











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             {
               "objectType": "HtmlForm",
               "mediaType": "application/x-www-form-urlencoded",
               "parameters": {
                 "foo": "http://example.org/FooProperty",
                 "bar": {
                   "objectType": "UrlTemplate",
                   "template": "http://example.org{/baz}",
                   "displayName": "Bar",
                   "required": false,
                   "repeated": false
                 }
               }
             }

   Likewise, when the value of a parameter is expected to be an instance
   of a specific MIME media type, the TypedPayload objectType
   (Section 8) can be used.

             {
               "objectType": "HtmlForm",
               "mediaType": "multipart/form-data",
               "parameters": {
                 "file": {
                   "objectType": "TypedPayload",
                   "mediaType": "image/*",
                   "repeated": true
                 }
               }
             }

11.  Authentication Object

   An Authentication Object is used by Action Handlers that require
   specific authentication options to be supported in order to carry out
   the Action.  The object is expresed as a JSON dictionary mapping
   authentication schema labels to JSON dictionaries that provide a
   specific description of properties and requirements specific to the
   scheme.












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   Example Authentication details:

     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note",
       "actions": {
         "view": {
           "objectType": "HttpActionHandler",
           "method": "GET",
           "url": "http://example.org/notes/1",
           "auth": {
             "basic": {
               "realm": "http://example.org"
             },
             "oauth": {
               "scopes": [
                 "some.oauth.scope",
                 "another.oauth.scope"
               ]
             }
           }
         }
       }
     }

   This specification does not define the authentication schemes or
   their associated properties.  Unrecognized authentication schemes MAY
   be ignored.  However, if an implementation fails to recognize any of
   the authentication schemes specified by an Action Handler, it might
   not be possible to successfully carry out the Action.

12.  Styles Object

   A Styles Object is used by EmbedActionHandlers to provide CSS style
   hints for the container within which embedded content is to be
   displayed.  The object is expressed as either a single JSON
   dictionary object mapping CSS property names to appropriate CSS
   values, or an array of JSON dictionary objects.  An optional "media"
   member can be included within the dictionary providing a CSS Media
   Query.










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   Example style hints:

   {
     "objectType": "note",
     "displayName": "A simple note object",
     "content": "This is a simple note.",
     "actions": {
       "view": {
         "objectType": "EmbedActionHandler",
         "content": "Some plain text content",
         "mediaType": "text/plain",
         "style": {
           "height": "100px",
           "width": "100px",
           "box-shadow": "10px 10px 5px #888888"
         }
       }
     }
   }

   Multiple style hints for specific media query targets:

   {
     "objectType": "note",
     "displayName": "A simple note object",
     "content": "This is a simple note.",
     "actions": {
       "view": {
         "objectType": "EmbedActionHandler",
         "content": "Some plain text content",
         "mediaType": "text/plain",
         "style": [
           {
             "media": "print",
             "height": "100px",
             "width": "100px",
             "box-shadow": "10px 10px 5px #888888"
           },
           {
             "media": "screen and (orientation: landscape)",
             "height": "100px",
             "width": "100px",
             "box-shadow": "10px 10px 5px #888888"
           }
         ]
       }
     }
   }



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13.  Security Considerations

   TBD

14.  IANA Considerations

   TBD

15.  Normative References

   [I-D.snell-activitystreams]
              Snell, J., "JSON Activity Streams 2.0", draft-snell-
              activitystreams-07 (work in progress), April 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC6570]  Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
              and D. Orchard, "URI Template", RFC 6570, March 2012.

   [W3C.REC-xmlschema-2-20041028]
              Biron, P. and A. Malhotra, "XML Schema Part 2: Datatypes
              Second Edition", World Wide Web Consortium Recommendation
              REC-xmlschema-2-20041028, October 2004,
              <http://www.w3.org/TR/2004/REC-xmlschema-2-20041028>.

Appendix A.  Using Action Handlers From Other Vocabularies

   The Activity Streams 2.0 Actions mechanism is specifically designed
   to allow Action Handlers from multiple vocabularies.

A.1.  Schema.org Actions Proposal

   Based on http://www.w3.org/wiki/images/b/b9/Actionsinschema.org.pdf:

















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     {
       "objectType": "video",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "watch": [
           {
             "objectType": "http://schema.org/WebPageHandler",
             "url": "http://movies.example.com/player?id=123"
           },
           {
             "objectType": "http://schema.org/AndroidHandler",
             "url": "http://movies.example.com/player?id=123",
             "package": "com.movies"
           }
         ]
       }
     }

A.2.  Google's "Actions in the Inbox"

   Based on https://developers.google.com/gmail/actions/reference/
   review-action:




























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     {
       "objectType": "note",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "review": {
           "objectType": "http://schema.org/ReviewAction",
           "review": {
             "objectType": "http://schema.org/Review",
             "itemReviewed": {
               "objectType": "http://schema.org/FoodEstablishment",
               "name": "Joe's Diner"
             },
             "reviewRating": {
               "objectType": "http://schema.org/Rating",
               "bestRating": "5",
               "worstRating": "1"
             }
           },
           "handler": {
             "objectType": "http://schema.org/HttpActionHandler",
             "url": "http://reviews.com/review?id=123",
             "requiredProperty": {
               "objectType": "http://schema.org/Property",
               "name": "review.reviewRating.ratingValue"
             },
             "method": "http://schema.org/HttpRequestMethod/POST"
           }
         }
       }
     }

A.3.  Mixing Vocabularies


















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     {
       "objectType": "video",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "watch": [
           {
             "objectType": "HttpActionHandler",
             "url": "http://movies.example.com/player?id=123",
             "target": "NEW"
           },
           {
             "objectType": "http://schema.org/AndroidHandler",
             "url": "http://movies.example.com/player?id=123",
             "package": "com.movies"
           }
         ]
       }
     }

A.4.  Example Drawing From Multiple Vocabularies

     {
       "objectType": "video",
       "displayName": "A Movie!",
       "displayName": "A simple note object",
       "content": "This is a simple note.",
       "actions": {
         "watch": [
           {
             "objectType": "EmbedActionHandler",
             "displayName": "HD",
             "mediaType": "video/mpeg",
             "url": "http://cdn.example.org?id=123amp;fmt=HD",
           },
           {
             "objectType": "EmbedActionHandler",
             "displayName": "SD",
             "mediaType": "video/mpeg",
             "url": "http://cdn.example.org?id=123&fmt=SD",
           },
           {
             "objectType": "application",
             "displayName": "Watch on Netflix",
             "url": "http://netflix.com..."
           }
         ],
         "like": {



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           "objectType": "EmbedActionHandler",
           "mediaType": "text/html",
           "url": "http://www.facebook.com/plugins/like.php...",
           "style": {
             "width": "150px",
             "height": "50px"
           }
         },
         "share": [
           {
             "objectType": "HttpActionHandler",
             "displayName": "Twitter",
             "url": "https://twitter.com/share?url=...",
             "target": "DIALOG"
           },
           {
             "objectType": "HttpActionHandler",
             "displayName": "Facebook",
             "url": "https://www.facebook.com/sharer/sharer.php?u=...",
             "target": "DIALOG"
           }
         ],
         "save": [
           {
             "objectType": "service",
             "id": "http://getpocket.com",
             "displayName": "Pocket",
             "context": {
               "url": "http://example.org/movie?id=123",
               "title": "A Movie!",
               "tags": "foo, bar, baz"
             }
           },
           {
             "objectType": "service",
             "id": "http://instapaper.com",
             "displayName": "Instapaper",
             "context": {
               "url": "http://example.org/movie?id=123",
               "title": "A Movie!",
               "selection": "An action movie!"
             }
           }
         ],
         "review": {
           "objectType": "HttpActionHandler",
           "displayName": "Rate this movie!",
           "url": "http://review.example.org/movie?id=123",



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           "method": "POST",
           "expects": {
             "objectType": "HtmlForm",
             "mediaType": "application/x-www-form-urlencoded",
             "parameters": {
               "rating": {
                 "maxInclusive": 5,
                 "minInclusive": 0,
                 "fractionDigits": 2,
                 "totalDigits": 3
                 "type": "float",
                 "displayName": "Rating"
               },
               "comments": {
                 "displayName": "Comments",
                 "type": "string",
                 "required": false
               }
             }
           }
         }
       }
     }

Authors' Addresses

   James M Snell
   IBM

   Email: jasnell@gmail.com


   Matthew Marum
   SugarCRM

   Email: mgmarum@gmail.com















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