System design as derivation via rewriting

Reusing provably correct (pieces of) software not only simplifies the task of designing correct software systems, but also decreases the costs of their development. The problem of designing a class (in the sense of object oriented programming methodology) which inherits from those of a given library and whose instances respond to given messages, is reduced to the problem of symbolically deriving a specification from another one using the interfaces of the given classes as productions. The standard algebraic specifications and productions are enriched with keywords which can place standard properties of operations, which can enhance the expressiveness of the specifications or which can guide the choice of productions and drive the search in the space of all derivable specifications