<xs:group name="ConceptDefinitionGroup">
    <xs:annotation>
        <xs:documentation>A group of properites required to define the concept</xs:documentation>
    </xs:annotation>
    <!-- rev3: name made optional in ConceptDefinitionGroup, elements made global, made PCL only-->
    <xs:sequence>
        <xs:choice minOccurs="0" maxOccurs="unbounded">
            <xs:element ref="name" />
            <xs:element ref="definition" />
            <xs:element ref="note" />
            <xs:element ref="facet" />
        </xs:choice>
    </xs:sequence>
</xs:group>