A compositional approach to software design

Component software models promote software development by the assembly of prefabricated, configurable and independently evolving building blocks. Although effective for systems implementation, this approach is inadequate for the creation of reusable and changeable software architectures. Design patterns address these shortcomings of component-based software development by capturing the formal and informal expertise that is necessary for a reusable solution to a recurring problem. However, so far, there is no methodical approach to providing these building blocks in a tangible, flexible and composable form. To address this limitation, we introduce design components, which are reified design patterns fitted for component software. We detail the activities of design composition and illustrate them as a process within a 3D space of concreteness, specificity and scope. To evaluate design components and put them into perspective, we discuss their contribution in respect to important software quality properties