how to plug RDF datastore with my server?

Hi,

i am a Masters student working  on a demo related to distributed
environment, i  donn know much about RDF so consider this demo as my
first step in learning more about RDF.   To be specific ,  in my demo i
have created 3 dataservers containing XML documents and a query server
to query the dataservers.. I want to plug RDF datastores with my
dataservers. How can i do it? the language that i am using is Java.
It will be of great help if anybody guides me , how to proceed in the
right direction.

Thanx in advance,
Best,
Erica