Object-oriented design patterns have been proposed as an approach to encapsulate good-quality design experiences that are proven useful in successful projects. They provide a higher level of abstraction than traditional object-oriented constructs such as classes and objects. A design pattern abstracts a solution structure that is mostly described in terms of a set of collaborating classes or objects. Composing these design structures to develop application designs is a tedious task that involves integration of patterns. We envisage that a tool-support for developing designs using patterns will facilitate the integration process. Current object-oriented modeling tools (including tools that support design patterns) do not explicitly support patterns as architecture constructs with interfaces.
In this paper, we describe a design environment for visual composition of design patterns for the purpose of developing pattern-oriented designs. The tool makes the notion of pattern interfaces explicit and integrates patterns at the architecture level. In addition to database search and retrieval, the tool supports three hierarchical traceable pattern-level design models, namely the Pattern-Level view, the Pattern Interfaces view, and the Detailed Pattern-Level view. The internal details of the pattern structure are hidden at high design levels (pattern views) and are traced to lower design levels (class views). Current visual modeling tools do not explicitly support the concepts of pattern views and pattern interfaces. The proposed tool facilitates the process of designing applications using patterns as design components, it integrates with existing object-oriented modeling tools, and it provides a mechanism to trace patterns through various levels of abstraction. We use an illustrative example to show how the tool can be used to develop pattern-oriented designs.'