RE: What good is Restriction?

> Here's a real simple 
> case (artificial,
> as it may be...I'm sure that given a few moments we could all 
> come up with a
> "useful" example) that illustrates the difficulty:
> 
> 	<xs:complexType name='base'>
> 		<xs:sequence>
> 			<xs:element name='a' minOccurs='0'>
> 				<xs:complexType>
> 					...
> 				</xs:complexType>
> 			</xs:element>
> 			<xs:element name='b'>
> 				<xs:complexType>
> 					<xs:sequence>
> 						<xs:element name='a'
> minOccurs='0'>
> 							<xs:complexType>
> 								...
> 							
> </xs:complexType>
> 						</xs:element>
> 					</xs:sequence>
> 				</xs:complexType>
> 			</xs:element>
> 		</xs:sequence>
> 	</xs:complexType>
> 
> If I write a restriction of 'base' that only mentions the element
> 'a'...which model does it refer to?

I thought XPaths were suggested as an alternative in this case. Why was that
rejected? It's used for keydefs.