A method of performing computer-based on-line commerce in which a client computer issues a group of interrelated commercial requests and each one of a plurality of server computers is available to service at least one of said requests, said method, performed by an intelligent agent, comprising steps of: receiving the group of interrelated commercial requests from said client computer; and finding servers which will satisfy said group of requests using client preference levels indicating for each request at least one preferred value which the client would like the agent to use in finding a server to satisfy that request; characterized in that said finding step also uses a client significance level indicating for a corresponding request the relative significance of this request in comparison to the other requests in the group.