A method and apparatus for interprocess message switching between a sender process and a plurality of receiver processes is disclosed. Messages supported comprise request and notice messages. Receiver processes supported comprise handler processes and observer processes. Request messages may be observed as well as handled, and notice messages may be handled as well as observed. Handler and observer processes may be non-executing as well as executing. Sender processes do not need to specify the identity of the receiver processes. The sender process and the receiver processes may be executed on the same computer or on two or more computers in a network.