<?xml version="1.0" encoding="UTF-8"?>
<grammar xmlns="http://relaxng.org/ns/structure/1.0"
         ns="http://www.aiai.ed.ac.uk/project/ix/"
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes">

  <!-- Hand-written grammar that has patterns for known constraints -->

  <include href="plan.rng">

    <!-- Redefine constraint to allow any type except "world-state" -->

    <define name="constraint">
      <element name="constraint">
	<optional>
	  <attribute name="type">
            <data type="string">
              <except>
                <value>world-state</value>
              </except>
            </data>
	  </attribute>
	</optional>
	<optional>
	  <attribute name="relation">
	    <ref name="symbol-value" />
	  </attribute>
	</optional>
	<optional>
	  <attribute name="sender-id">
	    <ref name="name-value" />
	  </attribute>
	</optional>
	<interleave>
	  <optional>
	    <element name="parameters">
	      <ref name="list" />
	    </element>
	  </optional>
	  <optional>
	    <element name="annotations">
	      <ref name="map" />
	    </element>
	  </optional>
	</interleave>
      </element>
    </define>

  </include>

  <define name="constraint" combine="choice">
    <ref name="known-constraint" />
  </define>

  <!-- world-state condition consraint -->

  <define name="known-constraint" combine="choice">
    <element name="constraint">
      <attribute name="type">
        <value>world-state</value>
      </attribute>
      <attribute name="relation">
        <value>condition</value>
      </attribute>
      <optional>
        <attribute name="sender-id">
          <ref name="name-value" />
        </attribute>
      </optional>
      <interleave>
        <element name="parameters">
          <element name="list">
            <ref name="pattern-assignment" />
          </element>
        </element>
        <optional>
          <element name="annotations">
            <ref name="map" />
          </element>
        </optional>
      </interleave>
    </element>
  </define>

  <!-- world-state effect consraint -->

  <define name="known-constraint" combine="choice">
    <element name="constraint">
      <attribute name="type">
        <value>world-state</value>
      </attribute>
      <attribute name="relation">
        <value>effect</value>
      </attribute>
      <optional>
        <attribute name="sender-id">
          <ref name="name-value" />
        </attribute>
      </optional>
      <interleave>
        <element name="parameters">
          <element name="list">
            <ref name="pattern-assignment" />
          </element>
        </element>
        <optional>
          <element name="annotations">
            <ref name="map" />
          </element>
        </optional>
      </interleave>
    </element>
  </define>

</grammar>
