atomactivity.xml

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<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
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<rfc category="exp" docName="atomactivity-00" ipr="none">
  <front>
    <title abbrev="AtomActivity">Atom Activity Extensions (Draft)</title>

    <author fullname="Martin Atkins" initials="M." surname="Atkins">
      <organization>Six Apart</organization>
    </author>

    <author fullname="David Recordon" initials="D." surname="Recordon">
      <organization>Facebook</organization>
    </author>

    <author fullname="Chris Messina" initials="C." surname="Messina">
      <organization>Citizen Agency</organization>
    </author>

    <author fullname="Monica Keller" initials="M." surname="Keller">
      <organization>Facebook</organization>
    </author>

    <author fullname="Ari Steinberg" initials="A." surname="Steinberg">
      <organization>Facebook</organization>
    </author>

    <author fullname="Rob Dolin" initials="R." surname="Dolin">
      <organization>Microsoft</organization>
    </author>

    <date />

    <abstract>
      <t>This document presents an extension that allows activities on social
      objects to be expressed within the Atom Syndication Format.</t>
    </abstract>

    <note title="Requirements Language">
      <t>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 <xref
      target="RFC2119">RFC 2119</xref>.</t>
    </note>
  </front>

  <middle>
    <section title="Introduction">
      <t>This document presents an extension that allows activities on social
      objects to be expressed within <xref target="RFC4287">the Atom
      Syndication Format</xref>.</t>
    </section>

    <section title="Notational Conventions">
      <t>The XML Namespaces URI [W3C.REC-xml-names-19990114] for the XML
      elements and attributes described in this specification is: <spanx
      style="verb">http://activitystrea.ms/spec/1.0/</spanx>.</t>

      <t>In this document, this namespace is referred to as "the AtomActivity
      namespace", and the namespace prefix "activity:" is used for the above
      namespace URI. The namespace prefix "atom:" is used for the namespace
      URI <spanx style="verb">http://www.w3.org/2005/Atom</spanx>. The
      namespace prefix "thr:" is used for the namespace URI <spanx
      style="verb">http://purl.org/syndication/thread/1.0</spanx>. The choices
      of namespace prefix are arbitrary and not semantically significant.</t>

      <t>This specification uses a shorthand form of terms from the XML
      Infoset [W3C.REC-xml-infoset-20040204]. The phrase "Information Item" is
      omitted when naming element and attribute information items. Therefore,
      when this specification uses the term "element," it is referring to an
      element information item in infoset terms. Likewise, when this
      specification uses the term "attribute," it is referring to an attribute
      information item.</t>

      <t>This specification allows the use of IRIs [RFC3987]. Every URI
      [RFC3986] is also an IRI, so a URI may be used wherever an IRI is named.
      When an IRI that is not also a URI is given for dereferencing, it MUST
      be mapped to a URI using the steps in Section 3.1 of [RFC3987]. When an
      IRI is serving as an identifier, it MUST NOT be so mapped.</t>

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

      <t>This specification uses "the Atom specification" to refer to <xref
      target="RFC4287"></xref>.</t>
    </section>

    <section title="Activity Concepts">
      <t>For the purpose of this specification, an activity is a description
      of an action that was performed (the verb) at some instant in time by
      some actor (the actor, as described in <xref
      target="activityactor"></xref> ), with some social object (the object).
      An activity feed is a feed of such activities.</t>

      <t>An activity may also have a target, which is the object into which or
      to which the action was done. Whether a target is allowed and the
      specific meaning of a target is defined by each verb.</t>

      <t>It is expected that in many cases consumers of activity feeds will
      use them to turn machine readable descriptions of activities into
      human-readable sentences such as "Joanne posted a Photo: 'My Cat'". The
      process for forming such sentences is not defined by this
      specification.</t>

      <section title="Verbs and Object Types">
        <t>Verbs and object types are identified by IRIs (verb and object
        identifiers) as defined by <xref target="RFC3987"></xref> though these
        IRIs MAY not resolve to any useful resource. One verb is defined by
        this specification in <xref target="postverb"></xref>.</t>

        <t>Other specifications MAY define further verb and object types with
        corresponding IRIs. Such specifications MUST define the meaning of
        these verb and object identifiers, and SHOULD also describe how any
        additional properties of the verb or object type are to be encoded in
        an Atom entry.</t>

        <t>Verbs and object types MAY derive from other verbs and object
        types. The properties required by the parents will also be required by
        the derived types. For example, if there is a base object type image
        and a derived type of photo, all properties that are defined for image
        are also defined for photo. Consumers that do not support the photo
        object type may use their recognition of the image object type as a
        fallback when processing an object of type photo.</t>
      </section>
    </section>

    <section anchor="activityentries" title="Activity Entries">
      <t>An activity entry is an entry element as described by the Atom
      specification that represents an activity. The actor of the activity
      entry is the author of the entry. The verbs and object of the activity
      are identified explicitly in the Activity entry as described in the
      following sections. An Atom entry is considered to be an activity entry
      if and only if it has at least one <spanx style="verb">activity:verb</spanx>
      child element and one or more <spanx style="verb">activity:object</spanx>
      child elements as described in the following sections.</t>

      <section anchor="titlesummarydetail"
               title="Activity Title, Summary and Detail">
        <t>In an activity entry, the <spanx style="verb">atom:title</spanx>,
        <spanx style="verb">atom:summary</spanx> and <spanx style="verb">atom:content</spanx>
        elements as described by <xref target="RFC4287"></xref> MUST contain a
        human-readable description of the activity. This text will be used by
        general Atom processors that do not understand this extension. This
        text MAY also be used by feed processors that do not recognize the
        verb. Any other non-activity elements may be used in an activity entry
        to effect a desired handling by non-activity processors.</t>

        <t>Feed producers MAY use information from outside sources to choose a
        suitable language to use for the activity description. For example, a
        feed producer responding to an HTTP request might use the HTTP
        Accept-Language header or a user preference otherwise determined to
        select a language. Feed producers SHOULD use <spanx style="verb">xml:lang</spanx>
        as described in <xref target="RFC4287"></xref> section 2 to identify
        the language used.</t>
      </section>

      <section title="Time of the Activity">
        <t>The time at which an activity occurred is represented in the
        atom:published element within each activity entry. An activity entry
        MUST have exactly one atom:published element.</t>

        <t>The time stored herein is the time that the activity occurred,
        <spanx>not</spanx> the time that the associated activity object was
        published. Feed processors MAY use this element to sort a list of
        activity entries into chronological order.</t>
      </section>

      <section title="Activity Link">
        <t>An activity entry SHOULD include an atom:link element with a link
        relationship of "alternate", a type of "text/html" and a href
        attribute containing the URL of an HTML-based representation of this
        activity or the associated object. Though this link does not have any
        special significance in this specification, general Atom processors
        that do not support the activity extensions will often present such a
        link to the user.</t>
      </section>

      <section anchor="activityverbelement" title="Activity Verb">
        <t>Verbs are represented using the activity:verb Extension Element.
        All activity entries MUST have at least one activity:verb element.</t>

        <t>The content of the activity:verb element MUST be a verb identifier
        (an IRI as defined by <xref target="RFC3987"></xref>). Note that the
        definition of IRI excludes relative references. Although the IRI MAY
        use a dereferencable scheme, processors must not assume that it can be
        dereferenced.</t>

        <t>The verb identifier within this element defines a verb for this
        activity. A given activity entry MAY have more than one activity:verb
        element, which indicates that there are several verbs describing this
        activity. Where multiple verbs are used, all verbs MUST be
        generalizations or specializations of one another. For example, the
        general verb "to experience" might be specialized by a verb "to listen
        to". If a derived verb is used, publishers SHOULD also include all of
        its ancestor types so that a consumer may use the most specific verb
        it understands.</t>

        <t>An activity feed processor SHOULD use the most specific verb it
        understands within each entry. If none of the activity's verbs are
        understood by the processor, the processor MAY use other information
        to infer the verb, or the processor MAY use the content of the
        atom:title, atom:summary and/or atom:content to obtain a
        human-readable description of the activity as a fallback.</t>

        <figure>
          <artwork><![CDATA[<entry>
<id>tag:versioncentral.example.org,2009:/commit/1643245</id>
<published>2009-06-01T12:54:00Z</published> 
<title>Geraldine committed a change to yate</title>
<content type="html">Geraldine just committed a change to yate on VersionCentral</content>
<link rel="alternate" type="text/html"
      href="http://versioncentral.example.org/geraldine/yate/commit/1643245" /> 
<activity:verb>http://activitystrea.ms/schema/1.0/post</activity:verb>
<activity:verb>http://versioncentral.example.org/activity/commit</activity:verb>
<activity:object>
  <activity:object-type>http://versioncentral.example.org/activity/changeset</activity:object-type> 
  <id>tag:versioncentral.example.org,2009:/change/1643245</id> 
  <title>Punctuation Changeset</title>
  <summary>Fixing punctuation because it makes it more readable.</summary> 
  <link rel="alternate" type="text/html" href="..." /> 
</activity:object>
</entry>]]></artwork>

          <postamble>Example: This example introduces a "changeset" object
          type and a "commit" verb, both ficticious, invented for the
          ficticious example service "VersionCentral". Since the "commit" verb
          is a derived type of "post", VersionCentral's activity entries
          include both the "post" verb and the "commit" verb so that consumers
          which do not support their proprietary extension may fall back on
          the "post" verb.</postamble>
        </figure>
      </section>

      <section anchor="activityobjectelement" title="Activity Object">
        <t>The object is represented using the activity:object extension
        element. The activity:object element contains information about the
        main object of the activity. All activity entries MUST have one or
        more activity:object elements. The content model of activity:object is
        identical to that of atom:entry when used to describe an object as
        described in <xref target="objectentries"></xref>.</t>

        <t>activity:object MUST contain exactly one atom:id element. If this
        object is also published elsewhere, the atom:id value SHOULD be the
        same in all representations.</t>

        <t>activity:object SHOULD contain exactly one atom:title element,
        whose value provides the human-readable display name for the
        object.</t>

        <t>activity:object SHOULD also contain exactly one atom:link element
        with a link relationship of "alternate" and the type "text/html", with
        the href attribute containing the URL of the HTML representation of
        the object if available.</t>

        <t>activity:object MAY also contain an atom:source element, as
        described by the Atom specification, describing the feed where this
        object resides. Processors MAY use this information to give context to
        the activity. If an atom:source element is not present, the feed which
        contains the object is the source.</t>

        <t>activity:object MAY also contain a thr:in-reply-to element, as
        described by <xref target="RFC4685"></xref>, identifying a second
        object that this object is considered to be in reply to.</t>

        <t>activity:object MAY contain additional elements whose meaning
        depends on the definition of the object types identified in the
        activity:object-type element as described in <xref
        target="objecttypeelement"></xref>.</t>

        <t>An activity entry and its associated object entry MUST NOT share
        the same atom:id value.</t>

        <t>If an activity entry contains more than one activity:object
        element, that activity entry represents several activities. These
        activities all share the same actor, target, verbs, and time
        but use each activity:object element in turn. When a set of activities
        is coalesced in this way it holds no special meaning to activity
        processors; it is intended to allow publishers to provide
        pre-coalesced activities to generic Atom consumers.</t>

        <section anchor="objecttypeelement"
                 title="The activity:object-type Extension Element">
          <t>The content of the activity:object-type element MUST be an object
          identifier (an IRI as defined by <xref target="RFC3987"></xref>).
          The definition of IRI excludes relative references. Though the IRI
          MAY use a dereferenceable scheme, processors MUST not assume that it
          can be dereferenced.</t>

          <t>The object identifier within this element gives an object type
          for the object described by this object entry. A given object entry
          MAY have more than one activity:object-type element, which indicates
          that this object has several types. Where multiple types are used,
          all types MUST be generalizations or specializations of one another.
          For example, the general type "web page" might be specialized by a
          type "weblog entry". If a derived type is used, publishers SHOULD
          also include all of its ancestor types so that a consumer may use
          the most specific type it understands.</t>

          <t>An object entry SHOULD have at least one activity:object-type
          element.</t>

          <t>Activity feed processors SHOULD use the most specific object type
          that they understand within each entry. The processor MAY use other
          information to infer the object type if it cannot understand any of
          the object types given. If it cannot so infer the object type, a
          processor MUST act as though no activity:object-type element is
          present.</t>

          <t>If no activity:object-type element is present, the object has no
          specific type. Processors SHOULD refer to such objects only by their
          titles. For example, when forming an activity sentence a processor
          might say "Johan posted 'My Cat'" rather than "Johan posted a photo:
          'My Cat'".</t>
        </section>
      </section>

      <section title="Activity Target">
        <t>The activity:target element contains information about the target
        of the activity, for verbs that support a target. The target is the
        object that the action was done to. The content model of <spanx
        style="verb">activity:target</spanx> and the meaning of its child
        elements are identical to that of <spanx style="verb">activity:object</spanx>.
        The precise meaning of the target as relates to the activity depends
        on the verb in use, but its meaning is somewhat similar to the English
        preposition "to". The activity:target extension element MUST NOT be
        used for indirect objects that are not targets.</t>

        <t>For example, in <xref target="activityentrycomplex"></xref> the
        target is a photo album to which photos were added.</t>
      </section>

      <section anchor="activityactor" title="Activity Actor">
        <t>
          The actor of an activity is identified by the atom:author element of the
          activity entry.  The Atom specification defines the atom:author element to
          identify the author of an entry, feed, or source feed.  This specification
          extends the object model of atom:author to include the additional elements
          defined for activity:object.
        </t>

        <t>
          If an activity entry does not contain an atom:author element, a consumer
          SHOULD use the atom:author of the contained atom:source element or of the
          containing atom:feed, as defined in Section 4.2.1 of the Atom specification.
        </t>

      </section>

      <section title="Activity Generator">
        <t>
          The atom:generator element is defined by the Atom specification as a
          feed-level element for identifying the agent used to generate a feed.
          This specification defines an additional use of the atom:generator
          element as a child element of an activity.  In this context, it
          identifies the agent used to create that individual activity entry.
        </t>

        <t>
          If an activity entry does not contain an atom:generator element, then
          the atom:generator of the contained atom:source element is considered to
          apply.  In an Activity Feed Document, the atom:generator element of the
          containing atom:feed element are considered to apply to the entry if
          there are no atom:generator elements in the locations described above.
        </t>
      </section>
    </section>

    <section anchor="objectentries" title="Object Entries">
      <t>An object entry is an entry element as described by the Atom
      specification that represents the object of an activity. Any entry that
      does not meet the criteria for being an activity entry as described in
      <xref target="activityentries"></xref> is considered an object entry by
      this specification. In particular, this means that a valid Atom entry
      without any activity annotations is considered to be an object entry by
      this specification.</t>

      <t>Object entries are intended to be used by feeds that describe the
      creation of content. In a valid object entry, all Atom elements SHOULD
      describe the object that was created or otherwise the object of an
      activity, rather than describing the activity itself.</t>

      <t>The content model of an object entry is the same as that of an <spanx
      style="verb">activity:object</spanx> element used within an activity
      entry, as defined in <xref target="activityobjectelement"></xref>.</t>

      <section anchor="impliedpost" title="Implied Activity">
        <t>When used alone, outside of the context of an explicit activity
        entry, an object entry has an implied activity. The implied activity
        entry for an object entry is constructed as follows:</t>

        <t><list style="numbers">
            <t>Create an empty atom:entry element. This is the activity entry
            element.</t>

            <t>If the object entry has as a child at least one activity:verb
            element, copy all such elements into the activity entry element.
            Otherwise, insert into the activity entry element a new
            activity:verb element containing the verb Identifier of the post
            verb as described in <xref target="postverb"></xref>.</t>

            <t>Copy the atom:published element from the object entry element
            into the activity entry element.</t>

            <t>Insert into the activity entry element a new activity:object
            element.</t>

            <t>Do a deep copy of all child elements of the object entry
            element into the activity:object element, excluding activity:verb
            and atom:published.</t>

            <t>If the activity entry has as a child an activity:verb element
            containing the verb Identifier of the post verb, copy the
            atom:published element from the object entry to the
            activity:object element.</t>
          </list></t>

        <t>Processors SHOULD generate suitable human-readable descriptions of
        the action and insert them as described in <xref
        target="titlesummarydetail"></xref>.</t>

        <t>If the resulting entry will be published, processors SHOULD
        generate suitable values for all other elements that the Atom
        specification requires as children of atom:entry. In particular, an
        atom:id value SHOULD be generated; this value MUST NOT be the same as
        that of the object entry's atom:id.</t>

        <t>If the resulting entry is to be published, processors MAY omit
        elements from the generated activity:object element to reduce
        overhead. Such processors SHOULD bear in mind the requirements in
        <xref target="activityobjectelement"></xref>.</t>

        <t>Processors expecting activity entries SHOULD apply the above
        transformation to any object entries they encounter in order to
        process them as activities, or at least act as if they have done
        so.</t>

        <t>Due to the way it is constructed, there is no way to represent
        additional properties for the verb(s) of an implied activity. If a
        particular verb requires additional properties then it MUST NOT be
        used in an implied activity.</t>

        <section title="The verbs for the Implied Activity">
          <t>When appearing as a child of an object entry (that is, an entry
          that does not also have an activity:object child element), the
          content of the <spanx style="verb">activity:verb</spanx> element
          MUST be the verb type of the implied activity for the object entry,
          as defined in <xref target="impliedpost"></xref>. When used in this
          way, the content model is identical to when used in an activity
          entry as described in <xref
          target="activityverbelement"></xref>.</t>
        </section>
      </section>

    </section>

    <section title="Activity Feeds">
      <t>This specification defines no required extensions to the atom:feed
      element as defined by the Atom specification. Therefore a standard Atom
      feed that contains only activity entries as defined above can be
      considered to be an activity feed. Processors MAY create an activity
      entry representing the implied post activity of an object entry (see
      <xref target="impliedpost"></xref>) in order to synthesize an activity
      feed from a traditional Atom feed.</t>

      <t>A feed MAY contain both activity and object entries.</t>

      <section title="A Note about Legacy Feeds">
        <t>This section is non-normative.</t>

        <t>The implied post activity as described in <xref
        target="impliedpost"></xref>, along with the advice about untyped
        object entries in <xref target="objectentries"></xref>, are together
        intended to provide a mechanism for processing traditional
        non-activity Atom feeds as Activity Feeds. At the time of writing this
        specification, most such feeds serve to describe the activity of
        posting an item such as a weblog entry or a photo.</t>

        <t>It is acknowledged, however, that there exist feeds that have other
        meanings, such as a list of a particular user's "favorite" objects.
        When applying the advice for processing feeds without activity
        extensions to such feeds, a processor will likely misinterpret the
        nature of the activity. In practice, however, it seems that most feeds
        of this kind include something in the title indicating their nature,
        so rendering such a misinterpreted activity to a sentence will lead to
        something such as <spanx>Joe posted "Funny Cats" in "Joe's Favorite Videos"</spanx>,
        which, while not ideal, is an acceptable result in situations where
        activities are primarily for human consumption.</t>
      </section>
    </section>

    <section anchor="postverb" title="The 'post' Verb">
      <t>This specification defines a single verb, which has the verb
      Identifier IRI <spanx style="verb">http://activitystrea.ms/schema/1.0/post</spanx>.</t>

      <t>This verb describes the act of posting or publishing an object on the
      web. The implication is that before this activity occurred the object
      was not posted, and after the activity has occurred it <spanx>is</spanx>
      posted or published.</t>

      <t>This verb is used when creating the Implied post activity for a
      standalone object entry that has no explicit verb. It MAY also be used
      as the value of activity:verb in an explicit activity entry.</t>

      <t>In an activity entry which has the 'post' verb, the value of the
      atom:published element SHOULD be the same as the atom:published element
      in the associated object entry.</t>

      <t>If an activity using this verb has an <spanx style="verb">activity:target</spanx>
      element, the target object is the collection in which the item was
      posted.</t>

      <t>The 'post' verb has no additional properties or modifiers.</t>
    </section>

    <section title="Requirements for Activity Re-publishers">
      <t>An activity re-publisher is any system that produces feeds that
      contain activities or objects that were obtained from another feed or
      feed-like data source. This section contains requirements for such
      systems that aim to allow consumers of such feeds to process the
      activities described in such feeds in a way similar to how they would
      have processed the activities when obtained directly from the source,
      and to allow consumers to detect duplicate activities or objects
      obtained via multiple feeds.</t>

      <t>An activity re-publisher may choose to produce either object entries
      or Activity Entries, except where the the re-publisher is re-publishing
      an activity entry, in which case the activity entry MUST be produced to
      avoid loss of information that cannot be expressed in an object
      entry.</t>

      <t>Where a re-publisher produces a full activity entry from a source
      object entry, the mapping process described in <xref
      target="impliedpost"></xref> MUST be used. A re-publisher MAY perform
      additional mapping steps when doing this conversion.</t>

      <t>Where a re-publisher produces a full activity entry from a source RSS
      object entry, the mapping process described in <xref
      target="rss"></xref> MUST be used. A re-publisher MAY perform additional
      mapping steps when doing this conversion.</t>

      <t>If a source object entry does not contain verb or object type
      information, a re-publisher MAY use information obtained elsewhere to
      synthesize appropriate verb or object type annotations.</t>

      <t>When a re-publisher reproduces a source activity entry, the publisher
      MUST copy the atom:id and atom:published elements from the source
      activity entry without modification, and MUST similarly preserve the
      contents of all elements in the AtomActivity namespace where these
      elements are used correctly as per this specification.  Additionally, 
      the re-publisher SHOULD copy the entry's atom:generator element without 
      modification, if present.</t>

      <t>When a re-publisher reproduces an entry, the atom:source element MUST
      be used in accordance with its definition in the Atom specification. A
      re-publisher SHOULD include as much information as possible from the
      source entry, paying special attention to data that is of significance
      to the object type(s) and/or verb(s) used on the entry where these are
      known to the re-publisher.</t>

      <t>When a re-publisher produces a feed of activities aggregated from
      multiple sources but known via some externally-obtained information to
      be by the same actor, even if that actor is represented by a different
      object in different source feeds, the re-publisher SHOULD create a
      feed-level atom:author element that describes the re-publisher's
      representation of the actor and then substitute this representation in
      any atom:author, activity:object or activity:target element known to
      represent the same actor.</t>
    </section>

    <section title="Security Considerations">
      <t>As this specification defines an extension to the Atom Syndication
      Format, it is subject to the same security considerations defined in
      <xref target="RFC4287"></xref>.</t>

      <t>
        Publishers or Consumers implementing Activity Streams as a stream
        of public data may also want to consider the potential for unsolicited
        commercial or malicious content and should take preventative measures
        to recognize such content and either identify it or not include it in
        their stream implementations.
      </t>

      <t>
        Publishers should take reasonable measures to make sure potentially
        malicious user input such as cross-site scripting attacks are not
        included in the Activity Streams data they publish.
      </t>

      <t>
        Consumers that re-emit ingested content to end-users MUST take
        reasonable measures if emitting ingested content to make sure
        potentially malicious ingested input is not re-emitted.
      </t>

      <t>
        Consumers that re-emit ingested content for crawling by search engines
        should take reasonable measures to limit any use of their site as a
        Search Engine Optimization loophole.  This may include converting
        un-trusted hyperlinks to text or including a rel="nofollow" attribute.
      </t>
    </section>

    <section title="IANA Considerations">
      <t>None.</t>
    </section>
  </middle>

  <back>
    <references title="Normative References">
      <reference anchor="RFC4287">
        <front>
          <title>The Atom Syndication Format</title>

          <author fullname="Mark Nottingham" initials="M."
                  surname="Nottingham">
            <organization></organization>
          </author>

          <author fullname="Robert Sayre" initials="R." surname="Sayre">
            <organization></organization>

            <address>
              <postal>
                <street></street>

                <city></city>

                <region></region>

                <code></code>

                <country></country>
              </postal>

              <phone></phone>

              <facsimile></facsimile>

              <email></email>

              <uri></uri>
            </address>
          </author>

          <date month="December" year="2005" />
        </front>
      </reference>

      <reference anchor="RFC4685">
        <front>
          <title>Atom Threading Extensions</title>

          <author fullname="James Snell" initials="J." surname="Snell">
            <organization></organization>
          </author>

          <date month="September" year="2006" />
        </front>
      </reference>

      <reference anchor="RFC2119">
        <front>
          <title>Key words for use in RFCs to Indicate Requirement
          Levels</title>

          <author fullname="Scott Bradner" initials="S." surname="Bradner">
            <organization></organization>
          </author>

          <date month="March" year="1997" />
        </front>
      </reference>

      <reference anchor="RFC3987">
        <front>
          <title>Internationalized Resource Identifiers (IRIs)</title>

          <author fullname="Martin Duerst" initials="M." surname="Duerst">
            <organization></organization>
          </author>

          <author fullname="Michel Suignard" initials="M." surname="Suignard">
            <organization></organization>

            <address>
              <postal>
                <street></street>

                <city></city>

                <region></region>

                <code></code>

                <country></country>
              </postal>

              <phone></phone>

              <facsimile></facsimile>

              <email></email>

              <uri></uri>
            </address>
          </author>

          <date month="January" year="2005" />
        </front>
      </reference>

      <reference anchor="RFC3339">
        <front>
          <title>Date and Time on the Internet: Timestamps</title>

          <author fullname="Graham Klyne" initials="G." surname="Klyne">
            <organization></organization>
          </author>

          <date month="July" year="2002" />
        </front>
      </reference>

      <reference anchor="RSS_2.0"
                 target="http://www.rssboard.org/rss-specification">
        <front>
          <title>Date and Time on the Internet: Timestamps</title>

          <author fullname="Graham Klyne" initials="G." surname="Klyne">
            <organization></organization>
          </author>

          <date month="July" year="2002" />
        </front>
      </reference>
    </references>

    <section title="Acknowledgements">
      <t>...</t>
    </section>

    <section title="Examples">
      <t>This appendix is non-normative. Where these examples include
      fragments of XML documents, assume the namespace declarations <spanx
      style="verb">xmlns="http://www.w3.org/2005/Atom" xmlns:activity="http://activitystrea.ms/spec/1.0/"</spanx>
      are in scope.</t>

      <section anchor="activityentryexample" title="Activity Entry Examples">
        <figure anchor="activityentrysimple">
          <preamble>A typical activity entry</preamble>

          <artwork><![CDATA[<entry>
   <id>tag:photopanic.example.com,2008:activity01</id>
   <title>Geraldine posted a Photo on PhotoPanic</title>
   <published>2008-11-02T15:29:00Z</published>
   <link rel="alternate" type="text/html"
     href="http://example.com/geraldine/activities/1" />
   <activity:verb>
      http://activitystrea.ms/schema/1.0/post
   </activity:verb>
   <activity:object>
      <id>tag:photopanic.example.com,2008:photo01</id>
      <title>My Cat</title>
      <published>2008-11-02T15:29:00Z</published>
      <link rel="alternate" type="text/html"
        href="http://example.com/geraldine/photos/1" />
      <activity:object-type>
          tag:atomactivity.example.com,2008:photo
      </activity:object-type>
      <source>
          <title>Geraldine's Photos</title>
          <link rel="self" type="application/atom+xml"
            href="http://example.com/geraldine/photofeed.xml" />
          <link rel="alternate" type="text/html"
            href="http://example.com/geraldine/" />
      </source>
   </activity:object>
   <content type="html">
       &lt;p&gt;Geraldine posted a Photo on PhotoPanic&lt;/p&gt;
       &lt;img src="/geraldine/photo1.jpg"&gt;
   </content>
</entry>]]></artwork>

          <postamble>This example shows a typical activity entry using the
          post verb defined by this specification and a hypothetical "photo"
          object type. It also demonstrates the use of atom:title and
          atom:content to provide fallback content for feed processors that do
          not support activity extensions. An activity stream application
          might render this entry into the sentence "Geraldine posted a photo
          titled 'My Cat' in Geraldine's Photos", with the photo title and the
          source feed title presented as links.</postamble>
        </figure>

        <figure anchor="activityentrycomplex">
          <artwork><![CDATA[<entry>
    <id>tag:photopanic.example.com,2009:/activity/4859568/PhotoAdd/2519358/2009171</id>
    <title type="text">Geraldine added two new photos to the My Pets album.</title>
    <published>2009-06-21T00:28:35Z</published>
    <author>
      <name>Geraldine</name>
      <uri>http://example.com/geraldine</uri>
      <id>tag:photopanic.example.com,2009:/Person/4859568</id>
      <activity:object-type>
        http://activitystrea.ms/schema/1.0/person
      </activity:object-type>
      <link rel="alternate" type="text/html"
        href="http://example.com/geraldine" />
    </author>
    <link rel="alternate" type="text/html"
      href="http://example.com/geraldine/activities/1234" />
    <content type="xhtml">...</content>
    <activity:target>
      <activity:object-type>http://activitystrea.ms/schema/1.0/photo-album</activity:object-type>
      <id>tag:photopanic.example.com,2009:/Photo_Album/2519358</id>
      <title>My Pets</title>
      <link rel="alternate" type="text/html"
            href="/geraldine/albums/pets" />
    </activity:target>
    <activity:object>
      <activity:object-type>http://activitystrea.ms/schema/1.0/photo</activity:object-type>
      <activity:object-type>http://activitystrea.ms/schema/1.0/image</activity:object-type>
      <id>tag:photopanic.example.com,2009:/Photo/2519358/60764840</id>
      <title>My Cat</title>
      <link rel="alternate" type="text/html"
            href="/geraldine/photos/1643" />
      <link rel="preview" type="image/jpeg"
            href="/geraldine/photos/1643/thumb.jpg" />
      <link rel="enclosure" type="image/jpeg"
            href="/geraldine/photos/1643/full.jpg" />
    </activity:object>
    <activity:object>
      <activity:object-type>http://activitystrea.ms/schema/1.0/image</activity:object-type>
      <activity:object-type>http://activitystrea.ms/schema/1.0/photo</activity:object-type>
      <id>tag:photopanic.example.com,2009:/Photo/2519358/60764844</id>
      <title></title>
      <link rel="alternate" type="text/html"
            href="/geraldine/photos/1634" />
      <link rel="preview" type="image/jpeg"
            href="/geraldine/photos/1634/thumb.jpg" />
      <link rel="enclosure" type="image/jpeg"
            href="/geraldine/photos/1634/full.jpg" />
    </activity:object>
</entry>]]></artwork>

          <postamble>Example: An activity entry showing the use of the actor,
          verb, object and target elements. Also illustrated is the use of
          multiple objects in a single activity entry, which serves as a
          shorthand for publishing multiple consecutive activities with the
          same verb and target.</postamble>
        </figure>
      </section>

      <section anchor="objectentryexample" title="Object Entry Example">
        <figure>
          <preamble>A simple object entry</preamble>

          <artwork><![CDATA[<entry>
   <id>tag:photopanic.example.com,2008:photo01</id>
   <title>My Cat</title>
   <published>2008-11-02T15:29:00Z</published>
   <link rel="alternate" type="text/html"
         href="/geraldine/photos/1" />
   <activity:object-type>
       tag:atomactivity.example.com,2008:photo
   </activity:object-type>
</entry>
]]></artwork>

          <postamble>This example shows an object entry describing the object
          referred to in the activity from <xref
          target="activityentryexample"></xref>. That example would also be an
          acceptable implied post activity for this entry, assuming that this
          entry were in a feed whose attributes match those of the atom:source
          in the activity entry example.</postamble>
        </figure>
      </section>
    </section>

    <section anchor="rss" title="Object Entries in RSS">
      <t>For compatibility with existing deployments, this specification
      also recommends a subset of the activity markup that may be used in <xref
      target="RSS_2.0">RSS 2.0</xref> feeds to add verb and object type
      annotations to objects published in RSS rather than Atom feeds.</t>

      <t>Objects published as RSS 2.0 <spanx style="verb">item</spanx>
      elements may use the <spanx style="verb">activity:verb</spanx> and
      <spanx style="verb">activity:object-type</spanx> elements with
      equivalent content models and semantics as described above for their
      use in Atom object entries.</t>

      <t>Activity processors should use the following process to construct the
      implied activity for an object entry published as an RSS 2.0 <spanx
      style="verb">item</spanx> element, or should act as if they have done
      so:</t>

      <t><list style="numbers">
          <t>Create an empty atom:entry element. This is the activity entry
          element.</t>

          <t>If the object entry has as a child at least one activity:verb
          element, copy all such elements into the activity entry element.
          Otherwise, insert into the activity entry element a new
          activity:verb element containing the verb Identifier of the post
          verb as described in <xref target="postverb"></xref>.</t>

          <t>If the object entry has a RSS <spanx style="verb">pubDate</spanx>
          element as a child, parse its content as per the RSS 2.0
          specification to obtain a date and time value. Create an <spanx
          style="verb">atom:published</spanx> element whose content is the
          serialization of this data and time value as described in <xref
          target="RFC3339"></xref>, and insert this element into the
          activity entry element.</t>

          <t>Insert into the activity entry element a new <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the object entry has as a child an RSS title element, create
          an atom:title element whose text content matches the text content
          of that element element and insert the new element into the <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the object entry has as a child a <spanx style="verb">content</spanx>
          element in the namespace <spanx style="verb">http://purl.org/rss/1.0/modules/content/</spanx>,
          create an <spanx style="verb">atom:content </spanx>element whose
          text content matches the text content of that element and which
          has the attribute <spanx style="verb">type</spanx> with the value
          <spanx style="verb">html</spanx>. Otherwise, if the object entry
          has as a child an RSS <spanx style="verb">description</spanx>
          element, create an <spanx style="verb">atom:content</spanx>
          element whose text content matches the text content of that
          element and which has the attribute <spanx style="verb">type</spanx>
          with the value <spanx style="verb">html</spanx>. In both cases,
          insert the created <spanx style="verb">atom:content</spanx>
          element into the <spanx style="verb">activity:object</spanx>
          element.</t>

          <t>If the object entry a RSS <spanx style="verb">link</spanx>
          element as as a child, create an <spanx style="verb">atom:link</spanx>
          element with a <spanx style="verb">href</spanx> attribute whose
          value is the text content of the RSS <spanx style="verb">link</spanx>
          element, and with a <spanx style="verb">type</spanx> attribute
          whose value is <spanx style="verb">text/html</spanx>. Insert the
          <spanx style="verb">atom:link</spanx> element into the <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the object entry has one or more RSS <spanx style="verb">enclosure</spanx>
          elements as children, create for each an <spanx style="verb">atom:link</spanx>
          element with a <spanx style="verb">href</spanx> attribute whose
          value is the text content of the <spanx style="verb">enclosure</spanx>
          element's <spanx style="verb">url</spanx> attribute, a <spanx
          style="verb">rel</spanx> attribute whose value is <spanx
          style="verb">enclosure</spanx>, a <spanx style="verb">type</spanx>
          attribute whose value is the text content of the <spanx
          style="verb">enclosure</spanx> element's <spanx style="verb">type</spanx>
          attribute, and a <spanx style="verb">length</spanx> attribute
          whose value is the text content of the <spanx style="verb">enclosure</spanx>
          element's <spanx style="verb">length</spanx> attribute. If any of
          these attributes are not present on the <spanx style="verb">enclosure</spanx>
          element, the equivalent attribute on the <spanx style="verb">atom:link</spanx>
          element MUST NOT be created. Insert the created <spanx
          style="verb">atom:link</spanx> elements into the <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the object entry has a <spanx>descendent</spanx> one or more
          <spanx style="verb">thumbnail</spanx> elements in the namespace
          <spanx style="verb">http://search.yahoo.com/mrss/</spanx>, create
          for each an <spanx style="verb">atom:link</spanx> element with a
          <spanx style="verb">href</spanx> attribute whose value is the text
          content of the <spanx style="verb">thumbnail</spanx> element's url
          attribute, a <spanx style="verb">rel</spanx> attribute whose value
          is <spanx style="verb">preview</spanx>, a <spanx style="verb">width</spanx>
          attribute in the namespace <spanx style="verb">http://purl.org/syndication/atommedia</spanx>
          whose value is the text content of the <spanx style="verb">thumbnail</spanx>
          element's <spanx style="verb">width</spanx> attribute, and a
          <spanx style="verb">height</spanx> attribute in the namespace
          <spanx style="verb">http://purl.org/syndication/atommedia</spanx>
          whose value is the text content of the <spanx style="verb">thumbnail</spanx>
          element's <spanx style="verb">height</spanx> attribute. If any of
          these attributes are not present on the <spanx style="verb">thumbnail</spanx>
          element, the equivalent attribute on the <spanx style="verb">atom:link</spanx>
          element MUST NOT be created. Insert the created <spanx
          style="verb">atom:link</spanx> elements into the <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the object entry has as a child an RSS <spanx style="verb">guid</spanx>
          element, create an <spanx style="verb">atom:id</spanx> element
          whose text content matches the text content of that element. If
          the <spanx style="verb">guid</spanx> element has an attribute
          <spanx style="verb">isPermaLink</spanx> with the value <spanx
          style="verb">true</spanx>, additionally create an <spanx
          style="verb">atom:link</spanx> element with a <spanx style="verb">href</spanx>
          attribute containing the text content of the <spanx style="verb">guid</spanx>
          element and a type attribute whose value is <spanx style="verb">text/html</spanx>.
          In both cases, insert the created element into the <spanx
          style="verb">activity:object</spanx> element.</t>

          <t>If the activity entry has as a child an <spanx style="verb">activity:verb</spanx>
          element containing the IRI of the post verb, copy the <spanx
          style="verb">atom:published</spanx> element from the activity
          entry to the <spanx style="verb">activity:object</spanx>
          element.</t>
        </list></t>

      <t>If the above procedure results in an activity entry that is not
      valid as per this specification or the Atom specification, processors
      should treat the result as they would had the invalid entry arrived in a
      real feed rather than having been synthesized.</t>
    </section>
  </back>
</rfc>
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