(newbie) - adding new properties to existing RDFs

hi all,
    I am relatively new to RDF. I want to find  if I can create new RDFs by extending (add new and more specific properties) to an existing one.  This way everyone who only understands the generic RDF can  still process the "new" or "extended" RDF without any problem. This would allow us to create a hierarchy of RDFs without going away from standard ones. Can i get pointers to resources if there are any ? 

Your help is very much appreciated.

Thanks in advance,

Dhananjay