[xml] Accessing {DTD, RelaxNG, X-Schema} Structure using libxml2

[Oliver Schonefeld <oschonef TechFak Uni-Bielefeld DE>]

Hi,

I am currently in need of parsing xml schema languages and using the result
to implement a validation for xml-like documents[1].
Basically I want to parse the grammar (DTD, RelaxNG or XSchema) and my
parser should be able to ask: given grammer a,
1) is element x valid in my current processing context y
2) is attribute x valid on element y
I tried to check the API docs, but it seems libxml does not allow this kind
of access pattern or only using xmlDocPtr structures.
Did I miss something? If not, does anybody know some alterantives?

Thanks,
Best Regards,
Oliver

P.S. Please keep me CC'd, since I am not (yet) subscribed to the list.

[1] We are talking "mutli-layered" xml here, meaning markup allowing
multible annotation layers. Something like SGML's CONCUR feature.
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