Abstract: In a data processing system a structure (50) called an I/O association is constructed. An I/O association (50) is a symmetric structure which allows not only consumer (52) of a service to locate the provider (54) of the service, but it also permits the converse. In some respects, an I/O channel (32) is only half of an association (50). The association (50) describes a targeted object (56) and provides the means (57) of locating the necessary procedures to operate on the target (56). The association (50) also describes a source object (58) that is held responsible for the requested operation, as well as the means (60) of locating and invoking procedures to report results to the source object (58).