Hi,

I'm sorry if this has been answered before (or if the answer should've been
obvious), but can someone tell me if the following XML Schema should be
considered valid:

<xs:schema xmlns="foo" xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="foo" id="foo">
	<xs:element name="Foo" type="FooType" />
	<xs:element name="Bar" type="BarType" />
	<xs:complexType name="FooType">
		<xs:attribute name="name" type="xs:string" use="optional"/>
	</xs:complexType>
	<xs:complexType name="BarType">
		<xs:complexContent>
			<xs:extension base="FooType">
				<xs:attribute name="name" type="xs:string"
use="required"/>
			</xs:extension>
		</xs:complexContent>
	</xs:complexType>
</xs:schema>

Is it allowed to override/redefine an attribute of a base type when deriving
by extension?

The reason I'm asking this is because I've noticed that several
implementations expose a different behavior here:

Altova XMLSpy">XMLSpy 2009:
Does not allow attribute to be "redefined" in the derived type.

Mono:
Allows attribute to be "redefined" if its use and type match the attribute
in
the base type.

Microsoft .NET:
Allows attribute to be "redefined".

Oracle Service Bus:
Allows attribute to be "redefined".

Any feedback is appreciated.

Gert