Auto-generate a DTD from multiple XML documents?

Everyone,

Several of us involved with Distributed Proofreaders and Project
Gutenberg are analyzing a number of TEI documents representing PG
etexts.

As part of the analysis, we'd like to find an application which will
autogenerate a minimal DTD (or schema) for validating a given set of
documents sharing the same root element.

I have seen several applications which will autogenerate a DTD for a
single XML document, but have not yet found one which will generate a
DTD representing a set of XML documents.

Of course, we prefer a "free" application for this one-time job, but
if there's a good commercial package, hopefully we can find someone
with a copy who'd be happy to volunteer running the job for us.

Thanks in advance.

Jon Noring