-*- rnc -*-

  RELAX NG Compact Syntax Grammar for the

  Atom Format Specification Version 11

-->

<grammar xmlns:xhtml="http://www.w3.org/1999/xhtml" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:s="http://www.ascc.net/xml/schematron" xmlns="http://relaxng.org/ns/structure/1.0" datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

  <start>

    <choice>

      <ref name="atomFeed"/>

      <ref name="atomEntry"/>

    </choice>

  </start>

  <define name="atomCommonAttributes">

    <optional>

      <attribute name="xml:base">

        <ref name="atomUri"/>

      </attribute>

    </optional>

    <optional>

      <attribute name="xml:lang">

        <ref name="atomLanguageTag"/>

      </attribute>

    </optional>

    <zeroOrMore>

      <ref name="undefinedAttribute"/>

    </zeroOrMore>

  </define>

  <define name="atomPlainTextConstruct">

    <ref name="atomCommonAttributes"/>

    <optional>

      <attribute name="type">

        <choice>

          <value>text</value>

          <value>html</value>

        </choice>

      </attribute>

    </optional>

    <text/>

  </define>

  <define name="atomXHTMLTextConstruct">

    <ref name="atomCommonAttributes"/>

    <attribute name="type">

      <value>xhtml</value>

    </attribute>

    <ref name="xhtmlDiv"/>

  </define>

  <define name="atomTextConstruct">

    <choice>

      <ref name="atomPlainTextConstruct"/>

      <ref name="atomXHTMLTextConstruct"/>

    </choice>

  </define>

  <define name="atomPersonConstruct">

    <ref name="atomCommonAttributes"/>

    <interleave>

      <element name="atom:name">

        <text/>

      </element>

      <optional>

        <element name="atom:uri">

          <ref name="atomUri"/>

        </element>

      </optional>

      <optional>

        <element name="atom:email">

          <ref name="atomEmailAddress"/>

        </element>

      </optional>

      <zeroOrMore>

        <ref name="extensionElement"/>

      </zeroOrMore>

    </interleave>

  </define>

  <define name="atomDateConstruct">

    <ref name="atomCommonAttributes"/>

    <data type="dateTime"/>

  </define>

  <define name="atomFeed">

    <element name="atom:feed">

      <s:rule context="atom:feed">

        <s:assert test="atom:author or not(atom:entry[not(atom:author)])">An atom:feed must have an atom:author unless all of its atom:entry children have an atom:author.</s:assert>

      </s:rule>

      <ref name="atomCommonAttributes"/>

      <interleave>

        <zeroOrMore>

          <ref name="atomAuthor"/>

        </zeroOrMore>

        <zeroOrMore>

          <ref name="atomCategory"/>

        </zeroOrMore>

        <zeroOrMore>

          <ref name="atomContributor"/>

        </zeroOrMore>

        <optional>

          <ref name="atomGenerator"/>

        </optional>

        <optional>

          <ref name="atomIcon"/>

        </optional>

        <ref name="atomId"/>

        <zeroOrMore>

          <ref name="atomLink"/>

        </zeroOrMore>

        <optional>

          <ref name="atomLogo"/>

        </optional>

        <optional>

          <ref name="atomRights"/>

        </optional>

        <optional>

          <ref name="atomSubtitle"/>

        </optional>

        <ref name="atomTitle"/>

        <ref name="atomUpdated"/>

        <zeroOrMore>

          <ref name="extensionElement"/>

        </zeroOrMore>

      </interleave>

      <zeroOrMore>

        <ref name="atomEntry"/>

      </zeroOrMore>

    </element>

  </define>

  <define name="atomEntry">

    <element name="atom:entry">

      <s:rule context="atom:entry">

        <s:assert test="atom:link[@rel='alternate'] or atom:link[not(@rel)] or atom:content">An atom:entry must have at least one atom:link element with a rel attribute of 'alternate' or an atom:content.</s:assert>

      </s:rule>

      <s:rule context="atom:entry">

        <s:assert test="atom:author or ../atom:author or atom:source/atom:author">An atom:entry must have an atom:author if its feed does not.</s:assert>

      </s:rule>

      <ref name="atomCommonAttributes"/>

      <interleave>

        <zeroOrMore>

          <ref name="atomAuthor"/>

        </zeroOrMore>

        <zeroOrMore>

          <ref name="atomCategory"/>

        </zeroOrMore>

        <optional>

          <ref name="atomContent"/>

        </optional>

        <zeroOrMore>

          <ref name="atomContributor"/>

        </zeroOrMore>

        <ref name="atomId"/>

        <zeroOrMore>

          <ref name="atomLink"/>

        </zeroOrMore>

        <optional>

          <ref name="atomPublished"/>

        </optional>

        <optional>

          <ref name="atomRights"/>

        </optional>

        <optional>

          <ref name="atomSource"/>

        </optional>

        <optional>

          <ref name="atomSummary"/>

        </optional>

        <ref name="atomTitle"/>

        <ref name="atomUpdated"/>

        <zeroOrMore>

          <ref name="extensionElement"/>

        </zeroOrMore>

      </interleave>

    </element>

  </define>

  <define name="atomInlineTextContent">

    <element name="atom:content">

      <ref name="atomCommonAttributes"/>

      <optional>

        <attribute name="type">

          <choice>

            <value>text</value>

            <value>html</value>

          </choice>

        </attribute>

      </optional>

      <zeroOrMore>

        <text/>

      </zeroOrMore>

    </element>

  </define>

  <define name="atomInlineXHTMLContent">

    <element name="atom:content">

      <ref name="atomCommonAttributes"/>

      <attribute name="type">

        <value>xhtml</value>

      </attribute>

      <ref name="xhtmlDiv"/>

    </element>

  </define>

  <define name="atomInlineOtherContent">

    <element name="atom:content">

      <ref name="atomCommonAttributes"/>

      <optional>

        <attribute name="type">

          <ref name="atomMediaType"/>

        </attribute>

      </optional>

      <zeroOrMore>

        <choice>

          <text/>

          <ref name="anyElement"/>

        </choice>

      </zeroOrMore>

    </element>

  </define>

  <define name="atomOutOfLineContent">

    <element name="atom:content">

      <ref name="atomCommonAttributes"/>

      <optional>

        <attribute name="type">

          <ref name="atomMediaType"/>

        </attribute>

      </optional>

      <attribute name="src">

        <ref name="atomUri"/>

      </attribute>

      <empty/>

    </element>

  </define>

  <define name="atomContent">

    <choice>

      <ref name="atomInlineTextContent"/>

      <ref name="atomInlineXHTMLContent"/>

      <ref name="atomInlineOtherContent"/>

      <ref name="atomOutOfLineContent"/>

    </choice>

  </define>

  <define name="atomAuthor">

    <element name="atom:author">

      <ref name="atomPersonConstruct"/>

    </element>

  </define>

  <define name="atomCategory">

    <element name="atom:category">

      <ref name="atomCommonAttributes"/>

      <attribute name="term"/>

      <optional>

        <attribute name="scheme">

          <ref name="atomUri"/>

        </attribute>

      </optional>

      <optional>

        <attribute name="label"/>

      </optional>

      <ref name="undefinedContent"/>

    </element>

  </define>

  <define name="atomContributor">

    <element name="atom:contributor">

      <ref name="atomPersonConstruct"/>

    </element>

  </define>

  <define name="atomGenerator">

    <element name="atom:generator">

      <ref name="atomCommonAttributes"/>

      <optional>

        <attribute name="uri">

          <ref name="atomUri"/>

        </attribute>

      </optional>

      <optional>

        <attribute name="version"/>

      </optional>

      <text/>

    </element>

  </define>

  <define name="atomIcon">

    <element name="atom:icon">

      <ref name="atomCommonAttributes"/>

      <ref name="atomUri"/>

    </element>

  </define>

  <define name="atomId">

    <element name="atom:id">

      <ref name="atomCommonAttributes"/>

      <ref name="atomUri"/>

    </element>

  </define>

  <define name="atomLogo">

    <element name="atom:logo">

      <ref name="atomCommonAttributes"/>

      <ref name="atomUri"/>

    </element>

  </define>

  <define name="atomLink">

    <element name="atom:link">

      <ref name="atomCommonAttributes"/>

      <attribute name="href">

        <ref name="atomUri"/>

      </attribute>

      <optional>

        <attribute name="rel">

          <choice>

            <ref name="atomNCName"/>

            <ref name="atomUri"/>

          </choice>

        </attribute>

      </optional>

      <optional>

        <attribute name="type">

          <ref name="atomMediaType"/>

        </attribute>

      </optional>

      <optional>

        <attribute name="hreflang">

          <ref name="atomLanguageTag"/>

        </attribute>

      </optional>

      <optional>

        <attribute name="title"/>

      </optional>

      <optional>

        <attribute name="length"/>

      </optional>

      <ref name="undefinedContent"/>

    </element>

  </define>

  <define name="atomPublished">

    <element name="atom:published">

      <ref name="atomDateConstruct"/>

    </element>

  </define>

  <define name="atomRights">

    <element name="atom:rights">

      <ref name="atomTextConstruct"/>

    </element>

  </define>

  <define name="atomSource">

    <element name="atom:source">

      <ref name="atomCommonAttributes"/>

      <interleave>

        <zeroOrMore>

          <ref name="atomAuthor"/>

        </zeroOrMore>

        <zeroOrMore>

          <ref name="atomCategory"/>

        </zeroOrMore>

        <zeroOrMore>

          <ref name="atomContributor"/>

        </zeroOrMore>

        <optional>

          <ref name="atomGenerator"/>

        </optional>

        <optional>

          <ref name="atomIcon"/>

        </optional>

        <optional>

          <ref name="atomId"/>

        </optional>

        <zeroOrMore>

          <ref name="atomLink"/>

        </zeroOrMore>

        <optional>

          <ref name="atomLogo"/>

        </optional>

        <optional>

          <ref name="atomRights"/>

        </optional>

        <optional>

          <ref name="atomSubtitle"/>

        </optional>

        <optional>

          <ref name="atomTitle"/>

        </optional>

        <optional>

          <ref name="atomUpdated"/>

        </optional>

        <zeroOrMore>

          <ref name="extensionElement"/>

        </zeroOrMore>

      </interleave>

    </element>

  </define>

  <define name="atomSubtitle">

    <element name="atom:subtitle">

      <ref name="atomTextConstruct"/>

    </element>

  </define>

  <define name="atomSummary">

    <element name="atom:summary">

      <ref name="atomTextConstruct"/>

    </element>

  </define>

  <define name="atomTitle">

    <element name="atom:title">

      <ref name="atomTextConstruct"/>

    </element>

  </define>

  <define name="atomUpdated">

    <element name="atom:updated">

      <ref name="atomDateConstruct"/>

    </element>

  </define>

  <define name="atomNCName">

    <data type="string">

      <param name="minLength">1</param>

      <param name="pattern">[^:]*</param>

    </data>

  </define>

  <define name="atomMediaType">

    <data type="string">

      <param name="pattern">.+/.+</param>

    </data>

  </define>

  <define name="atomLanguageTag">

    <data type="string">

      <param name="pattern">[A-Za-z]{1,8}(-[A-Za-z0-9]{1,8})*</param>

    </data>

  </define>

    Unconstrained; it's not entirely clear how IRI fit into

    xsd:anyURI so let's not try to constrain it here

  -->

  <define name="atomUri">

    <text/>

  </define>

  <define name="atomEmailAddress">

    <data type="string">

      <param name="pattern">.+@.+</param>

    </data>

  </define>

  <define name="simpleExtensionElement">

    <element>

      <anyName>

        <except>

          <nsName ns="http://www.w3.org/2005/Atom"/>

        </except>

      </anyName>

      <text/>

    </element>

  </define>

  <define name="structuredExtensionElement">

    <element>

      <anyName>

        <except>

          <nsName ns="http://www.w3.org/2005/Atom"/>

        </except>

      </anyName>

      <choice>

        <group>

          <oneOrMore>

            <attribute>

              <anyName/>

            </attribute>

          </oneOrMore>

          <zeroOrMore>

            <choice>

              <text/>

              <ref name="anyElement"/>

            </choice>

          </zeroOrMore>

        </group>

        <group>

          <zeroOrMore>

            <attribute>

              <anyName/>

            </attribute>

          </zeroOrMore>

          <group>

            <optional>

              <text/>

            </optional>

            <oneOrMore>

              <ref name="anyElement"/>

            </oneOrMore>

            <zeroOrMore>

              <choice>

                <text/>

                <ref name="anyElement"/>

              </choice>

            </zeroOrMore>

          </group>

        </group>

      </choice>

    </element>

  </define>

  <define name="extensionElement">

    <choice>

      <ref name="simpleExtensionElement"/>

      <ref name="structuredExtensionElement"/>

    </choice>

  </define>

  <define name="undefinedAttribute">

    <attribute>

      <anyName>

        <except>

          <name>xml:base</name>

          <name>xml:lang</name>

          <nsName ns=""/>

        </except>

      </anyName>

    </attribute>

  </define>

  <define name="undefinedContent">

    <zeroOrMore>

      <choice>

        <text/>

        <ref name="anyForeignElement"/>

      </choice>

    </zeroOrMore>

  </define>

  <define name="anyElement">

    <element>

      <anyName/>

      <zeroOrMore>

        <choice>

          <attribute>

            <anyName/>

          </attribute>

          <text/>

          <ref name="anyElement"/>

        </choice>

      </zeroOrMore>

    </element>

  </define>

  <define name="anyForeignElement">

    <element>

      <anyName>

        <except>

          <nsName ns="http://www.w3.org/2005/Atom"/>

        </except>

      </anyName>

      <zeroOrMore>

        <choice>

          <attribute>

            <anyName/>

          </attribute>

          <text/>

          <ref name="anyElement"/>

        </choice>

      </zeroOrMore>

    </element>

  </define>

  <define name="anyXHTML">

    <element>

      <nsName ns="http://www.w3.org/1999/xhtml"/>

      <zeroOrMore>

        <choice>

          <attribute>

            <anyName/>

          </attribute>

          <text/>

          <ref name="anyXHTML"/>

        </choice>

      </zeroOrMore>

    </element>

  </define>

  <define name="xhtmlDiv">

    <element name="xhtml:div">

      <zeroOrMore>

        <choice>

          <attribute>

            <anyName/>

          </attribute>

          <text/>

          <ref name="anyXHTML"/>

        </choice>

      </zeroOrMore>

    </element>

  </define>

</grammar>