A Tool and a Formalism to Design and Apply Patterns

Pattern systems are becoming more and more numerous. They offer product patterns or process patterns of varied range and cover (analysis, design or implementation patterns, and general, domain or enterprise patterns). New application development environments have been developed together with these pattern-oriented approaches. These tools address two kinds of actors: patterns engineers who specify pattern systems, and applications engineers who use these systems to specify information systems. Most of the existing development environments are made for applications engineers; they offer few functionalities allowing definition and organization of pattern systems. This paper presents AGAP, a development environment for defining and using patterns, which distinguishes pattern formalisms from pattern systems. Not only does AGAP address applications engineers, but it also allows patterns engineers to define pattern systems. The same formalisms or items of existing formalisms may either be used in order to facilitate the engineering of pattern systems or to increase the level of reuse. We illustrate the use of AGAP by the presentation of P-Sigma, a common formalism for pattern representation. P-Sigma expresses a semantics common to most of the existing formalisms and standardizes the expression of product patterns and process patterns. It allows to clarify the patterns selection interface and facilitates the organization of pattern systems. Two pattern systems developed during industrial experimentation validate the P-Sigma formalism and were implemented in AGAP.