1. In a system having a client computer system and a service provider computer system programmed with a service implementation, an apparatus comprising: a service level agreement manager disposed between the client computer system and the service implementation, the service level agreement manager comprising: an admission controller configured to control admission of the client computer system to the service implementation using a service level agreement; a performance measurement module in communication with the admission controller and configured to measure performance of the service implementation; and a specification module in communication with the admission controller and with the performance measurement module.