When I try to parse the vxml.xsd schema from Voice XML I get the error:

C:\XML\VXMLSchema\vxml-schema>xsdobjectgen vxml.xsd /n:name
.NET Framework XSD Schema compile error.
Error occurred : Schema Validation Error: Reference to undeclared substitution g roup affiliation. An error occurred at file:///C:/XML/VXMLSchema/vxml-schema/synthesis-core.xsd, (372, 3).

I'm using XSDObjectGen from Microsoft and I don't know the reason of this error.

Thanks.