This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Would it make sense to modify the DatabaseException so that it extended IOException. That way you could declare the DataInterface methods so that they only threw IOException instead of both RemoteException and DatabaseException. The reason I say this is at the moment the client has to have code to deal with RemoteExceptions even when running in local mode when they would never be thrown.