This is a means to separate out a schema into multiple files, if I understand Gregor correctly he's asking for a way to test for id/keyref uniqueness across multiple files?

Yes, and data files, not schema/dtd. One xml data file defines ids, the other points to these ids. In the case of descriptive data, 1000s of item description files should all point to the same, centrally defined character definitions.

At a higher level there is XInclude which allows for including content from one document into another. Not sure on current support for this however.

I think this comes closest. Can you point me to information on XInclude? As you say, it seems unclear whether a validating parser, say msxml 4.0 would be able to check such id/idrefs.

Gregor ---------------------------------------------------------- Gregor Hagedorn (G.Hagedorn@bba.de) Institute for Plant Virology, Microbiology, and Biosafety Federal Research Center for Agriculture and Forestry (BBA) Koenigin-Luise-Str. 19 Tel: +49-30-8304-2220 14195 Berlin, Germany Fax: +49-30-8304-2203

Often wrong but never in doubt!