[xml-dev] Schema Validation

Hello XML gurus,

I have a set of XML files..say N.Based on some filters I need to load up
a subset (abt N/4 files for example).
There are elements in these N/4 files which refer to elements defined in
one of these N/4 files. 

Lets say N=20 and N/4=5 (f1,f2,f3,f4,f5)
So, Element A defined in file f5 can refer to ELement B defined in one
of the files f1,f2,f3,f4,f5. If element B is not defined in one of the 5
files, then thats an error condition for me. Can I use the schema
definitions to turn on checking for the above constraint.

Let me know if the problem statement is not clear.Any solution or
pointers to a solution would be greatly appreciated.

Thanks,
-Susheel.