<xs:schema xmlns="http://www.isr.uci.edu/projects/xadl3/schemas/structure-3.0.xsd"
            xmlns:xs="http://www.w3.org/2001/XMLSchema"
            xmlns:core="http://www.isr.uci.edu/projects/xadl3/schemas/xadlcore-3.0.xsd"
            targetNamespace="http://www.isr.uci.edu/projects/xadl3/schemas/structure-3.0.xsd"
            xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"
            elementFormDefault="qualified"
            attributeFormDefault="qualified"
            version="3.0.0"
            
            ecore:package="edu.uci.isr.xadl3.structure_3_0">

	<xs:import namespace="http://www.isr.uci.edu/projects/xadl3/schemas/xadlcore-3.0.xsd"
	           schemaLocation="http://www.isr.uci.edu/projects/xadl3/schemas/xadlcore-3.0.xsd"/>
	<xs:import namespace="http://www.eclipse.org/emf/2002/Ecore"
	           schemaLocation="http://www.isr.uci.edu/projects/xadl3/schemas/Ecore.xsd"/>

	<xs:annotation>
		<xs:documentation>

			xADL 3 Structure Schema

			This schema defines the basic elements that make up architectural
			structure: components, connectors, interfaces, links, and
			the scaffolding necessary for hierarchical modeling.  This schema
			is intentionally neutral about the semantics of these elements;
			semantics should be provided in extension schemas.

			Changelog:
			  - 3.0.0
			    * Initial version
			
		</xs:documentation>
	</xs:annotation>

	<!-- TOP LEVEL ELEMENT: archStructure -->

	<xs:element name="archStructure" type="ArchStructure" 
	            substitutionGroup="core:topLevelElement">
		<xs:annotation>
			<xs:documentation>
				This element is a top-level xADL element
				containing an architectural structure.
				A single document may contain more than one
				structure, and structures may be connected
				to one another via links in substructure
				relationships.
			</xs:documentation>
		</xs:annotation>
	</xs:element>
	
	<!-- COMPLEX TYPE: ArchStructure -->
	
	<xs:complexType name="ArchStructure">
		<xs:annotation>
			<xs:documentation>
				This type defines an architectural structure.
				A structure consists of components, connectors,
				and links.  Components and connectors internally
				contain interfaces.  It is possible for one
				structure to be nested within a component
				or connector by reference through the use of
				the subStructure element on components or
				connectors.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="component" type="Component"
			            minOccurs="0" maxOccurs="unbounded"/>
			<xs:element name="connector" type="Connector"
			            minOccurs="0" maxOccurs="unbounded"/>
			<xs:element name="link" type="Link"
			            minOccurs="0" maxOccurs="unbounded"/>
			<xs:element name="ext" type="core:Extension"
			            minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID"/>
		<xs:attribute name="name" type="xs:string"/>
	</xs:complexType>
		
	<!-- ENUMERATION TYPE: Direction -->
	
	<xs:simpleType name="Direction">
		<xs:annotation>
			<xs:documentation>
				This enumeration defines legal interface directions.
				
				They are:
				 - none:  No directionality selected or implied.
				 - in:    Incoming interface. Provided services
				          should be "in" interfaces.
				 - out:   Outgoing interface. Required services
				          should be "out" interfaces.
				 - inout: Incoming AND outgoing interface.
				          Endpoint both provides and requires
				          a service.
			</xs:documentation>
		</xs:annotation>
		<xs:restriction base="xs:string">
			<xs:enumeration value="none"/>
			<xs:enumeration value="in"/>
			<xs:enumeration value="out"/>
			<xs:enumeration value="inout"/>
		</xs:restriction>
	</xs:simpleType>
	
	<!-- COMPLEX TYPE: Interface -->
	
	<xs:complexType name="Interface">
		<xs:annotation>
			<xs:documentation>
				An interface is a point through which a brick
				(component or connector) communicates with the
				outside world. In general, required and provided
				services will be associated with interfaces.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="ext" type="core:Extension"
			            minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID"/>
		<xs:attribute name="name" type="xs:string"/>
		<xs:attribute name="direction" type="Direction"/>
	</xs:complexType>

	<!-- COMPLEX TYPE: Brick -->
	
	<xs:complexType name="Brick" abstract="true">
		<xs:annotation>
			<xs:documentation>
				Brick is the abstract base type for components
				and connectors.  A brick is a logical element
				that has an ID, a human-readable name, and
				zero or more interfaces.  Additionally, a brick
				may have internal substructure.  This type is
				defined so that, on a basic level, components
				and connectors can be treated equally.
				However, no BrickExtension type is defined,
				since we assume that there will be very
				semantically different extensions for
				components, connectors, and future types of
				bricks.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="interface" type="Interface"
			            minOccurs="0" maxOccurs="unbounded"/>
            <xs:element name="subStructure" type="SubStructure"
                        minOccurs="0" maxOccurs="1"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID"/>
		<xs:attribute name="name" type="xs:string"/>
	</xs:complexType>

	<!-- COMPLEX TYPE: Component -->

	<xs:complexType name="Component">
		<xs:annotation>
			<xs:documentation>
				Components are the loci of computation in an
				architecture.  They inherit all the properties
				of a Brick: ID, name, interfaces, and optional
				substructure.
			</xs:documentation>
		</xs:annotation>
		
		<xs:complexContent>
			<xs:extension base="Brick">
				<xs:sequence>
					<xs:element name="ext" type="core:Extension"
					            minOccurs="0" maxOccurs="unbounded"/>
				</xs:sequence>
			</xs:extension>
		</xs:complexContent>
	</xs:complexType>
	
	<!-- COMPLEX TYPE: Connector -->

	<xs:complexType name="Connector">
		<xs:annotation>
			<xs:documentation>
				Connectors are the loci of communication in an
				architecture.  They inherit all the properties
				of a Brick: ID, name, interfaces, and optional
				substructure.
			</xs:documentation>
		</xs:annotation>
		
		<xs:complexContent>
			<xs:extension base="Brick">
				<xs:sequence>
					<xs:element name="ext" type="core:Extension"
					            minOccurs="0" maxOccurs="unbounded"/>
				</xs:sequence>
			</xs:extension>
		</xs:complexContent>
	</xs:complexType>
	
	<!-- COMPLEX TYPE: SubStructure -->
	
	<xs:complexType name="SubStructure">
		<xs:annotation>
			<xs:documentation>
				This type allows the specification of
				sub-structure for a brick (component or connector);
				that is, the internal structure of a Brick can
				also contain its own structure of components
				and connectors.  This allows for hierarchical
				(and possibly recursive) composition.
				
				A subStructure consists of a link to the inner
				structure, alone with zero or more interface mappings.
				Interface mappings map (or connect) interfaces on the
				outer components and connectors with interfaces on
				the inner components and connectors.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="innerStructureLink" type="core:SimpleLink"/>
			<xs:element name="interfaceMapping" type="InterfaceMapping"
			            minOccurs="0" maxOccurs="unbounded"/>
			<xs:element name="ext" type="core:Extension"
			            minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID" use="required"/>
	</xs:complexType>

	<!-- COMPLEX TYPE: InterfaceMapping -->
	
	<xs:complexType name="InterfaceMapping">
		<xs:annotation>
			<xs:documentation>
				Interface mappings are used in the specification of
				sub-structure for a Brick (Component or Connector).
				An interface mapping maps (or connects) an interface
				on the outer Brick to an interface on an inner Brick.
				The outerInterfaceLink is a link to the interface
				on the outer brick.  The innerInterfaceLink is
				a link to the interface on the inner brick.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="outerInterfaceLink" type="core:SimpleLink"/>
			<xs:element name="innerInterfaceLink" type="core:SimpleLink"/>
			<xs:element name="ext" type="core:Extension"
			            minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID" use="required"/>
		<xs:attribute name="name" type="xs:string"/>
	</xs:complexType>
	
	<!-- COMPLEX TYPE: Link -->
	
	<xs:complexType name="Link">
		<xs:annotation>
			<xs:documentation>
				A Link is an architectural construct that
				connects two elements.  In general, it will
				connect two interfaces, although depending on
				the architectural rules in use, it may directly 
				connect two coarse-grained elements such as 
				Bricks.
				
				Links are intended to have very limited semantics:
				they simply indicate an association between two
				endpoints. If the connection needs to have
				deeper semantics, consider interposing a connector
				between the endpoints, since connectors are intended
				to be semantically-rich elements.
			</xs:documentation>
		</xs:annotation>
		
		<xs:sequence>
			<xs:element name="point1" type="core:SimpleLink"/>
			<xs:element name="point2" type="core:SimpleLink"/>
			<xs:element name="ext" type="core:Extension"
			            minOccurs="0" maxOccurs="unbounded"/>
		</xs:sequence>
		<xs:attribute name="id" type="xs:ID" use="required"/>
		<xs:attribute name="name" type="xs:string"/>
	</xs:complexType>

</xs:schema>