XML schema extensibility : new facet ?

Dear all,

I'm currently involved in the MPEG-7 DDL definition which
relies on XML Schema. We need to define a new facet for list
named 'dim' which specifies a multidimensionnal matrices.

It is desirable that a specific MPEG7 parser uses this new
facet while keeping a certain level of interoperability with a
classical XML-schema parser. At the very best, the XML
Schema could simply ignore the facet.

I just want to know if the best way is to use <appInfo>:

<simpleType name="matrix2x2OfInteger">
    <list base="integer">
        <annotation><appinfo>
                <mpeg7:dim value="2 2"/>
        </appinfo></annotation>
    </list>
</complexType>

Or would it be possible to define a new facet by subtyping the
xml-schema the definition of list (in the schema of the schemas),
and using the substitution mechanism in order to directly add
this new facet. It might seem crazy at a first glance.

<simpleType name="matrix2x2OfInteger">
    <mpeg7:list base="integer">
        <mpeg7:dim value="2 2"/>
    </mpeg7:list>
</simpleType>

Thank you for your response.

Best regards,

Cedric Thienot,
ExpWay, Paris

Received on Thursday, 5 October 2000 05:45:24 UTC