Since the Eclipse RCP front-end would actually be a remote front-end, we needed some kind of kind of communication between the client and the server. One of our first idea's was to use XML-RPC, which is pretty well supported in Grails, but it would force us to to do some mapping between our domain and the XML. Since we wanted to use the same domain classes is Eclipse as in Grails (by exporting the Grails domain to external domain jars), we opted for a different approach: Burlap/Hessian.