Microsoft test WildZ013 purports to be an invalid schema (it requires an inexpressible wildcard union). This union becomes expressible in XSD 1.1 (indeed, all unions are expressible in XSD 1.1), and the validity therefore needs to change.

Note: the schema test file is named test328873i.xsd. The union in question is between the two attribute groups:

<xs:attributeGroup name="attG1-54">
     <xs:anyAttribute namespace="##other" processContents="lax"/>
 </xs:attributeGroup>

 <xs:attributeGroup name="attG2-54">
     <xs:anyAttribute namespace="##local b c" processContents="lax"/>
 </xs:attributeGroup>

and the union is constructed under clause 5.2 of 3.10.6.3 Attribute Wildcard Union, and is effectively not(a).