Architectural Styles, Design Patterns, And Objects

Architectural styles, object-oriented design, and design patterns all hold promise as approaches that simplify software design and reuse by capturing and exploiting system design knowledge. This article explores the capabilities and roles of the various approaches, their strengths, and their limitations. oftware system builders increasingly recognize the importance of exploiting design knowledge in the engineering of new systems. Several distinct but related approaches hold promise. One approach is to focus on the architectural level of system design—the gross structure of a system as a composition of interacting parts. Architectural designs illuminate such key issues as scaling and portability, the assignment of functionality to design elements, interaction protocols between elements, and global system properties such as processing rates, end-to-end capacities, and overall performance.1 Architectural descriptions tend to be informal and idiosyncratic: box-and-line diagrams convey essential system structure, with accompanying prose explaining the meaning of the symbols. Nonetheless, they provide a critical staging point for determining whether a system can meet its essential requirements, and they guide implementers in constructing the system. More recently, architectural descriptions have been used for codifying and reusing design knowledge. Much of their power comes from use of idiomatic architectural terms, such as “clientserver system,” “layered system,” or “blackboard organization.”