<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:owlx="http://www.w3.org/2003/05/owl-xml" 
    xmlns:swrlx="http://www.w3.org/2003/11/swrlx" 
    xmlns:ruleml="http://www.w3.org/2003/11/ruleml"
    targetNamespace="http://www.w3.org/2003/11/swrlx"
    elementFormDefault="qualified"
    attributeFormDefault="qualified">

  <xsd:import namespace="http://www.w3.org/2003/05/owl-xml"
              schemaLocation="owlx/schema/owl1-dl.xsd" />

  <xsd:import namespace="http://www.w3.org/2003/11/ruleml"
              schemaLocation="ruleml.xsd" />

  <xsd:annotation>
    <xsd:documentation>
      XML Schema driver for SWRL 0.6
      The root element of SWRL documents for the XML
      Concrete Syntax must be the Ontology element. 
    </xsd:documentation>
  </xsd:annotation>

  <xsd:element name="Ontology"> 
    <xsd:annotation>
      <xsd:documentation>
        This is the root element of SWRL documents 
        in the XML Concrete Syntax.  It extends owlx:Ontology
      </xsd:documentation>
    </xsd:annotation>
    <xsd:complexType> 
      <xsd:sequence>
        <xsd:sequence minOccurs="0" maxOccurs="unbounded">
          <xsd:choice>
            <!-- Header elements --> 
            <xsd:element ref="owlx:VersionInfo" />
            <xsd:element ref="owlx:PriorVersion"  />
            <xsd:element ref="owlx:BackwardCompatibleWith" />
            <xsd:element ref="owlx:IncompatibleWith" />
            <xsd:element ref="owlx:Imports" />
            <xsd:element ref="owlx:Annotation" />

            <!-- Class elements --> 
            <xsd:element ref="owlx:Class" />
            <xsd:group   ref="owlx:classElements" />
  
            <!-- Property elements --> 
            <xsd:element ref="owlx:DatatypeProperty" />
            <xsd:element ref="owlx:ObjectProperty" />
            <xsd:element ref="owlx:SubPropertyOf" />
            <xsd:element ref="owlx:EquivalentProperties" /> 
   
            <!-- Instances --> 
            <xsd:element ref="owlx:Individual" />
            <xsd:element ref="owlx:SameIndividual" />
            <xsd:element ref="owlx:DifferentIndividuals" />

            <!-- SWRL extensions -->
            <xsd:element ref="ruleml:imp" />
            <xsd:element ref="ruleml:var" />
          </xsd:choice>
        </xsd:sequence>
      </xsd:sequence>
      <xsd:attribute ref="owlx:name" />
    </xsd:complexType>

    <!-- XXX:  clone for rule names, etc. -->
    <xsd:unique name="classNameUniqueness"> 
      <xsd:annotation>
        <xsd:documentation>
          This constraint ensures that every class name is unique 
          in a single OWL document. 
        </xsd:documentation>
      </xsd:annotation>
      <xsd:selector xpath="owlx:Class" /> 
      <xsd:field xpath="@owlx:name" /> 
    </xsd:unique>
  </xsd:element>

  <xsd:group name="atom">
    <xsd:choice>
      <xsd:element ref="swrlx:classAtom" />
      <xsd:element ref="swrlx:datarangeAtom" />
      <xsd:element ref="swrlx:individualPropertyAtom" />
      <xsd:element ref="swrlx:datavaluedPropertyAtom" />
      <xsd:element ref="swrlx:sameIndividualAtom" />
      <xsd:element ref="swrlx:differentIndividualAtom" />
      <xsd:element ref="swrlx:builtinAtom" />
    </xsd:choice>
  </xsd:group>

  <xsd:element name="classAtom">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:group ref="owlx:description" />
        <xsd:group ref="swrlx:iObject" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="datarangeAtom">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:group ref="owlx:datarange" />
        <xsd:group ref="swrlx:dObject" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="individualPropertyAtom">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:group ref="swrlx:iObject" />
        <xsd:group ref="swrlx:iObject" />
      </xsd:sequence>
      <xsd:attribute name="property" type="owlx:IndividualPropertyName" use="required" />
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="datavaluedPropertyAtom">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:group ref="swrlx:iObject" />
        <xsd:group ref="swrlx:dObject" />
      </xsd:sequence>
      <xsd:attribute name="property" type="owlx:DataPropertyName" use="required" />
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="sameIndividualAtom">
    <xsd:complexType>
      <xsd:sequence minOccurs="0" maxOccurs="unbounded">
        <xsd:group ref="swrlx:iObject" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="differentIndividualAtom">
    <xsd:complexType>
      <xsd:sequence minOccurs="0" maxOccurs="unbounded">
        <xsd:group ref="swrlx:iObject" />
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name="builtinAtom">
    <xsd:complexType>
      <xsd:sequence>
        <xsd:group ref="swrlx:dObject" minOccurs="1" maxOccurs="unbounded" />
      </xsd:sequence>
    <xsd:attribute name="builtin" type="swrlx:BuiltinName" use="required" />
    </xsd:complexType>
  </xsd:element>

  <xsd:group name="iObject">
    <xsd:choice>
      <xsd:element ref="owlx:Individual" />
      <xsd:element ref="ruleml:var" />
    </xsd:choice>
  </xsd:group>

  <xsd:group name="dObject">
    <xsd:choice>
      <xsd:element ref="owlx:DataValue" />
      <xsd:element ref="ruleml:var" />
    </xsd:choice>
  </xsd:group>

  <xsd:simpleType name="BuiltinName">
    <xsd:restriction base="xsd:anyURI" />
  </xsd:simpleType>

</xsd:schema>