Abstract: A knowledge-based system comprising a plurality of knowledge processors each of which includes a knowledge base and performs a reasoning process for replying to a request from a user, and a file server which is connected to the knowledge processors through a transmission line. When each knowledge processor cannot resolve the user's request with the knowledge base of its own, it sends a request message to the other processor or processors through the transmission line. Reply messages from the other knowledge processors complying with the request message are managed in correspondence with the requests by the file server which receives the reply messages, and when a predetermined condition has been established, a reply is given to the knowledge processor which is the source of the request.