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Formal Specification and Verification of Design Patterns

This chapter introduces our approaches to formal specification of the structural and behavioral aspects of Design patterns. We investigate the logic-based formalisms in our specification methods and demonstrate the applications of these methods in examples. Our formal specifications methods not only help for rigorous, precise, and unambiguous descriptions of Design patterns, but also allow us to verify the consistencies of Design pattern applications and compositions. Dong, Alencar, & Cowan Copyright © 2007, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Introduction A Design pattern (Gamma, Helm, Johnson, & Vlissides, 1995) documents expert solutions to a recurring problem in a particular context. Design patterns are then applied in many applications to improve the quality of the resulting software system and the productivity of the associated personnel. Thus, the specification and description of Design patterns are critical to their successful application. Design patterns are typically described informally to facilitate understanding by software developers. However, there are several drawbacks to the informal representation of Design patterns. First, informal specifications may be ambiguous, and Design patterns may not be able to be expressed precisely in an informal language. Second, informal representation may not be amendable to rigorous analysis. Each Design pattern may have some particular properties that characterize it, and the application of a Design pattern should maintain these properties. Formal specification allows the use of automated tools to check such properties. Third, formal specifications of Design patterns also form the basis for the discovery of Design patterns in large software systems. Rigorous descriptions of Design patterns allow reverse engineering tools and techniques to be built to discover the Design patterns used in a design. We have investigated several approaches to the formal specification of Design patterns and their composition in the past decade. In particular, we separated the structural and behavioral aspects of Design patterns and proposed specification methods based on first-order logic, temporal logic, temporal logic of action, process calculus, and Prolog. We also explored verification techniques based on theorem proving. The main objective of this chapter is to describe our investigations on formal specification techniques for Design patterns, and then demonstrate using these specifications as the methods of reasoning about Design pattern properties when they are used in software systems.