In the medical diagnosis system, the client -side inference engine guides patient through relevant questions based on the given symptoms. Fig.5 shows an instance frame Basic Questions which is created from a class frame Basic Question. The user specifies the earache symptom and the corresponding slot value is set to true. The If Change attached procedure of the slot will refer to the frame instance “symptoms to earache” which leads to further information on the patient. Finally, patient information frame instances are created. It will be submitted to the knowledge base system on the server side for further inference.