Seam App accessing data via an EJB
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I have to investigate the possibility of using JBoss and Seam to build user interfaces to data held in a database controlled by an off-the-shelf package. I've been reading through some of the Seam documentation, and various other sources, but I can't seem to clear the confusion I'm currently suffering from.
 
My problem is that everything I've read so far talks about using JPA/Hibernate to access and persist data directly in a database schema, but the package I'm working with doesn't allow (or actively discourages) direct updates to any schema that it controls. It does however present what looks like a comprehensive data-access API delivered as an EJB. With the basic assumption that it's entirely possible, my question is how would I go about building a Seam app that uses this EJB for all data access? Is it a simple thing or am I heading for a whole heap of pain? Can anyone point me in the direction of reading material that will help me?  
 
Apologies in advance for the newbie nature of this question, but I've been dropped in at the deep end on this and I'm struggling to pick up so much new knowledge. Any help will be **very** gratefully received.
 
Many  thanks
 
Steve