A frame-based expert system uses set of rules for inference. Rules are facets in slots. There is a trigger mechanism that checks activities on a slot. If add, if need, if change and if remove are typical facets which take action when slot value is manipulated. In the FORXDB system, forward chaining is employed. Since the system has 2 inference engines, one on the client side and another one on the knowledge base (knowledge server) side, inference can be done on both sides. The client side first takes care of user interaction to obtain current information interactively while the server side takes care of the inference from recorded or historical information.