<xsd:schema xmlns="http://www.ics.uci.edu/pub/arch/xArch/implementation.xsd"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            xmlns:archinst="http://www.ics.uci.edu/pub/arch/xArch/instance.xsd"
            xmlns:archtypes="http://www.ics.uci.edu/pub/arch/xArch/types.xsd"
            xmlns:archvariants="http://www.ics.uci.edu/pub/arch/xArch/variants.xsd"
            targetNamespace="http://www.ics.uci.edu/pub/arch/xArch/implementation.xsd"
            elementFormDefault="qualified"
            attributeFormDefault="qualified">

  <!-- Import namespaces used -->
  <xsd:import namespace="http://www.ics.uci.edu/pub/arch/xArch/instance.xsd"
              schemaLocation="http://www.isr.uci.edu/projects/xarchuci/core/instance.xsd"/>
  <xsd:import namespace="http://www.ics.uci.edu/pub/arch/xArch/types.xsd"
              schemaLocation="http://www.isr.uci.edu/projects/xarchuci/ext/types.xsd"/>
  <xsd:import namespace="http://www.ics.uci.edu/pub/arch/xArch/variants.xsd"
              schemaLocation="http://www.isr.uci.edu/projects/xarchuci/ext/variants.xsd"/>

  <xsd:annotation>
    <xsd:documentation>
      xArch Implementation Stub XML Schema 1.0
      
      Depends on: {types.xsd, variants.xsd}
         Note: The actual dependency set of this extension is
         just types, but because of XML Schema 1.0's single
         inheritance model, we also extend variants
         so that a component/connector type may have both 
         variants and an implementation.
         
      Change Log:
         2004-07-16: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Changed cardinality of implementation element
           on types from 0-1 to 0+.
         2002-07-23: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Changed location of core (xArch) schema in the import
           statement to a more stable URL.
         2002-01-28: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Upgraded to 2001 XML Schema standard and validated
           with XML Spy 4.2.  Only changes were to the namespace
           declaration for 'xsd' in the header.
         2001-04-12: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Cleaned up and validated with XML Spy 3.5.
         2000-12-05: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Changed "Variable*Type" to "Variant*Type" to match
           variants.xsd specification.  Thanks to Nathan D.
           Ryan [Nathan.Ryan@colorado.edu].
         2000-10-16: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Adapted to work with new instances/types model,
           changed dependency so it depends on variants and
           types (see notes above).
         2000-09-28: Eric M. Dashofy [edashofy@ics.uci.edu]:
           Initial Development and validated with XSV

    </xsd:documentation>
  </xsd:annotation>

  <!--
    TYPE: Implementation

    The Implementation type is abstract at this level because
    it is important to establish its place in the XML-trees
    at this point (namely, a sub-element of Component, Connector,
    and Interface Types), but given the wide range of implementation
    technologies available, it is not possible to anticipate
    all of them.  So, in lieu of that, the Implementation
    type provides a hook that can be realized via an extension
    such as 'JavaImplementation' or 'DCOMImplementation', etc.
    with all details necessary to comprehend the implementation
    of a given component.
   -->
  <xsd:complexType name="Implementation" abstract="true"/>
  
  <!--
    TYPE: VariantComponentTypeImpl
    
    The VariantComponentTypeImpl type extends the VariantComponentType
    type to add the ability to add an optional implementation specification 
    to a component type.  If all instantiated components, connectors,
    and interfaces have types with specified implementations, it
    should be possible to start a running system.
   -->
  <xsd:complexType name="VariantComponentTypeImpl">
    <xsd:complexContent>
      <xsd:extension base="archvariants:VariantComponentType">
        <xsd:sequence>
          <xsd:element name="implementation" type="Implementation"
                       minOccurs="0" maxOccurs="unbounded"/>
        </xsd:sequence>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>

  <!--
    TYPE: VariantConnectorTypeImpl 
    
    The VariantConnectorTypeImpl type extends the VariantConnectorType 
    type to add the ability to add an optional implementation specification 
    to a connector type.  If all instantiated components, connectors,
    and interfaces have types with specified implementations, it
    should be possible to start a running system.
   -->
  <xsd:complexType name="VariantConnectorTypeImpl">
    <xsd:complexContent>
      <xsd:extension base="archvariants:VariantConnectorType">
        <xsd:sequence>
          <xsd:element name="implementation" type="Implementation"
                       minOccurs="0" maxOccurs="unbounded"/>
        </xsd:sequence>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>
  
  <!--
    TYPE: InterfaceTypeImpl
    
    The InterfaceTypeImpl type extends the InterfaceType
    type to add the ability to add an optional implementation specification 
    to an interface type.  If all instantiated components, connectors,
    and interfaces have types with specified implementations, it
    should be possible to start a running system.
   -->
  <xsd:complexType name="InterfaceTypeImpl">
    <xsd:complexContent>
      <xsd:extension base="archtypes:InterfaceType">
        <xsd:sequence>
          <xsd:element name="implementation" type="Implementation"
                       minOccurs="0" maxOccurs="unbounded"/>
        </xsd:sequence>
      </xsd:extension>
    </xsd:complexContent>
  </xsd:complexType>
  
</xsd:schema>