Service channels-purpose and tradeoffs

Claims concerning the maintainability of object oriented software usually refer to encapsulation and inheritance mechanisms. However if objects are perceived only from the code level, potentials for higher level maintenance operations are missed. Moreover classical maintenance focussing just on code destroys the relationship that once existed between specification and implementation. The authors present service channels as mechanisms to support maintenance requests on the specification and, for a substantial class of requests, the propagation to the implementation keeping the relationships between specification and implementation consistent