<?xml version="1.0" encoding="utf-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0">

  <start>
    <ref name="Metadata" />
  </start>

  <define name="MetaMeta"
          ns="http://plone.org/ns/archetypes/"
          xmlns="http://relaxng.org/ns/structure/1.0">
    <optional>
      <attribute name="filename" />
    </optional>
    <optional>
      <attribute name="content_type" />
    </optional>
    <optional>
      <attribute name="transfer_encoding" />
    </optional>
  </define>

  <define name="DublinCore"
          xmlns:dc="http://purl.org/dc/elements/1.1/"
          datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
          xmlns="http://relaxng.org/ns/structure/1.0">
    <choice>
      <zeroOrMore>
        <element name="dc:title"><text /></element>
      </zeroOrMore>
      <zeroOrMore>
        <element name="dc:description">
          <ref name="MetaMeta" />
          <text />
        </element>
      </zeroOrMore>
      <zeroOrMore>
        <element name="dc:subject"><text /></element>
      </zeroOrMore>
      <zeroOrMore>
        <element name="dc:contributor"><data type="string" /></element>
      </zeroOrMore>
      <oneOrMore>
        <element name="dc:creator"><data type="string" /></element>
      </oneOrMore>
      <zeroOrMore>
        <element name="dc:language"><data type="language" /></element>
      </zeroOrMore>
      <zeroOrMore>
        <element name="dc:rights">
          <ref name="MetaMeta" />
          <text />
        </element>
      </zeroOrMore>
    </choice>
  </define>

  <define name="DateInfo"
          xmlns:xmp="adobe:ns:meta"
          datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
          xmlns="http://relaxng.org/ns/structure/1.0">
        <zeroOrMore>
          <element name="xmp:CreateDate"><data type="dateTime" /></element>
        </zeroOrMore>
        <zeroOrMore>
          <element name="xmp:ModifyDate"><data type="dateTime" /></element>
        </zeroOrMore>
  </define>

  <define name="ArchetypesFields"
          ns="http://plone.org/ns/archetypes/"
          xmlns:note="atxml:annotations"
          datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
          xmlns="http://relaxng.org/ns/structure/1.0">
    <element name="field">
      <note:info>
        All non-standard Archetypes fields are represented by a 'field'
        element, their id specified by an attribute 'id'.
      </note:info>
      <attribute name="id" />
      <ref name="MetaMeta" />
      <choice>
        <text />
        <zeroOrMore>
          <element name="reference">
            <note:info>
              References can be made by UID (Archetypes),
              relative path, or by specifying a group of values
              that can uniquely identify a piece of content.
            </note:info>
            <choice>
              <zeroOrMore>
                <element name="uid"><text /></element>
              </zeroOrMore>
              <zeroOrMore>
                <element name="path"><text /></element>
              </zeroOrMore>
              <zeroOrMore>
                <ref name="Metadata" />
              </zeroOrMore>
            </choice>
          </element>
        </zeroOrMore>
      </choice>
    </element>
  </define>


  <define name="Metadata">
    <element name="metadata" ns="http://plone.org/ns/archetypes/"
             xmlns:cmf="http://cmf.zope.org/namespaces/default/"
             datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes"
             xmlns="http://relaxng.org/ns/structure/1.0">
      <!-- does not explicitly allow 'xml:lang' attribute -->
      <interleave>
        <optional>
          <element name="cmf:type"><text /></element>
        </optional>
        <optional>
          <element name="uid"><text /></element>
        </optional>
        <zeroOrMore>
          <ref name="DublinCore" />
        </zeroOrMore>
        <zeroOrMore>
          <ref name="DateInfo" />
        </zeroOrMore>
        <zeroOrMore>
          <ref name="ArchetypesFields" />
        </zeroOrMore>
      </interleave>
    </element>
  </define>

</grammar>
