Design guidelines for “tailorable” frameworks

. Since the early eighties, object-oriented frameworks have demonstrated that one can encapsulate a reusable, tailorable software architecture as a collection of collaborating, extensible object classes. Such frameworks are particularly important for the development of open systems, where not only functionality, but also architecture must be reused across a family of related applications. Unfortunately, the design of frameworks remains an art rather than a science, because of the inherent conflict between flexibility --- packaging software components that can be reused in as many contexts as possible --- and tailorability --- designing software architectures that are easy to adapt to targeted requirements. To cope with this conflict, well-designed object-oriented frameworks must provide a clean conceptual framework that clearly identifies so-called hot spots where flexibility is necessary and desirable, and specifies framework contracts that formalize in exactly what way the...