Integrating XHTML modules into a markup language

I wish to utilize some XHTML modules in a schema I am developing. If, for 
example I wish to include the Block structural module - which if I 
understand correctly is called xhtml-blkstruct-1.xsd - where should I be 
referencing this from?

One of the places I have tried it from here: 
http://www.w3.org/MarkUp/SCHEMA/xhtml-blkstruct-1.xsd and I get a 'missing 
Common.attrib attribute group' error. Before I go about trying to debug this 
I feel I am going about this in the wrong way?

Thanks in advance

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