Database components integration, ontologies

I'd like to have some informations about Component integration, schema integration in databases !
Is there anyone who treats this subject ? Because I need it for my research thesis.

It's about integrating two or more Information systems components then assemble there in one schema.

I also need to consider ontological aspects...

I know it can be done also with XML but theorically and practically I don't see how can I do it, then I have to write my thesis about this, but for the moment I couldn't do anything productive, I have been working in this subject during 4 months now and I have only 2 months more to achieve my work.
Please help me, what can I do.

Thank you very much for your help !!!!