A method of brokering network services by identifying a service which is complementary to a first service, the first service having an associated first service description comprising first service identification information identifying the service offered and first interface type information, the first interface type information comprising at least one of an input format accepted by the first service and an output format generated by the first service, the method comprising the steps of; identifying a second service having an associated second service description comprising second service identification information identifying the service offered and second interface type information which is complementary to the first interface type information, and modifying the first service description in accordance with the second service description.