Class Composition for Specifying Framework Design

Object-oriented frameworks are a particularly appealing approach towards software reuse. An object-oriented framework represents a design for a family of applications, where variations in the application domain are tackled by filling in the so-called hot spots. However, experience has shown that the current object-oriented mechanisms (class inheritance and object composition) are not able to elegantly support the "fill in the hot spot" idea. This paper introduces class composition as a more productive approach towards hot spots, offering all of the advantages of both class inheritance and object composition but involving extra work for the framework designer.