XML Include

Hi!
 I need to include a XML file into another, as my XML files are starting to grow big and I need to maintain different files now. My XML files have been defined with respect to a schema, and not with a DTD. I need the syntax of the XML Include construct, with respect to a schema.
I tried using the DOCTYPE, and ENTITY construct, but the schema processor somehow doesn't locate the file and starts cribbing.
Also since there would be too many datasets that I will be handling, I need a construct to include multiple XML files.
I hope I have been clear in stating my requirements ;-).
Any leads?

Suchir Sen