<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0" 
         xmlns:ann="http://relaxng.org/ns/compatibility/annotations/1.0"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">
  <start>
      <ref name="element-rule"/>
  </start>

  <define name="element-rule">
    <element name="rule">
     <choice>
     <attribute name="id-ref"><data type="IDREF"/></attribute>
     <group>
      <attribute name="id"><data type="ID"/></attribute>
      <choice>
        <externalRef href="score.rng"/>
        <attribute name="score-attribute"><text/></attribute>
      </choice>
      <optional>
        <attribute name="boolean-op">
          <choice>
            <value>or</value>
            <value>and</value>
          </choice>
        </attribute>
      </optional>
      <optional>
        <attribute name="role"><text/></attribute>
      </optional>
      <oneOrMore>
        <choice>
          <element name="expression">
            <attribute name="id"><data type="ID"/></attribute>
            <attribute name="attribute"><text/></attribute>
            <attribute name="operation">
              <choice>
                <value>lt</value>
                <value>gt</value>
                <value>lte</value>
                <value>gte</value>
                <value>eq</value>
                <value>ne</value>
                <value>defined</value>
                <value>not_defined</value>
              </choice>
            </attribute>
            <optional>
              <attribute name="value"><text/></attribute>
            </optional>
            <optional>
              <attribute name="type" ann:defaultValue="string">
                <choice>
                  <value>string</value>
                  <value>number</value>
                  <value>version</value>
                </choice>
              </attribute>
            </optional>
            <optional>
              <attribute name="value-source" ann:defaultValue="literal">
                <choice>
                  <value>literal</value>
                  <value>param</value>
                  <value>meta</value>
                </choice>
              </attribute>
            </optional>
          </element>
          <element name="date_expression">
            <attribute name="id"><data type="ID"/></attribute>
            <choice>
              <group>
                <attribute name="operation"><value>in_range</value></attribute>
                <choice>
                  <group>
                    <optional>
                      <attribute name="start"><text/></attribute>
                    </optional>
                    <attribute name="end"><text/></attribute>
                  </group>
                  <group>
                    <attribute name="start"><text/></attribute>
                    <element name="duration">
                      <ref name="date-common"/>
                    </element>
                  </group>
                </choice>
              </group>
              <group>
                <attribute name="operation"><value>gt</value></attribute>
                <attribute name="start"><text/></attribute>
              </group>
              <group>
                <attribute name="operation"><value>lt</value></attribute>
                <choice>
                  <attribute name="end"><text/></attribute>
                </choice>
              </group>
              <group>
                <attribute name="operation"><value>date_spec</value></attribute>
                <element name="date_spec">
                  <ref name="date-common"/>
                </element> 
              </group>
            </choice>
          </element> 
          <ref name="element-rule"/>
        </choice>
      </oneOrMore>
     </group>
     </choice>
    </element>
  </define>

  <define name="date-common">
    <attribute name="id"><data type="ID"/></attribute>
    <optional>
      <attribute name="hours"><text/></attribute>
    </optional>
    <optional>
      <attribute name="monthdays"><text/></attribute>
    </optional>
    <optional>
      <attribute name="weekdays"><text/></attribute>
    </optional>
    <optional>
      <attribute name="yearsdays"><text/></attribute>
    </optional>
    <optional>
      <attribute name="months"><text/></attribute>
    </optional>
    <optional>
      <attribute name="weeks"><text/></attribute>
    </optional>
    <optional>
      <attribute name="years"><text/></attribute>
    </optional>
    <optional>
      <attribute name="weekyears"><text/></attribute>
    </optional>
    <optional>
      <attribute name="moon"><text/></attribute>
    </optional>
  </define>

</grammar>