4 Comparison

A number of ADLs and supporting tools have been developed, which include Aesop [GAO94], Rapide [LKAVBM95], UniCon [SDKRYZ95], Wright [AlGa94], STILE [StWe87] and so on. Aesop is a system for developing style-specific architecture development environments, i.e. it supports the use of architectural styles. Rapide is an event-based, concurrent, object-oriented language, which allows architectural design to be simulated and analyzed. UniCon supports architectural abstractions for describing different types of components and connectors. Wright supports specifications and analysis of interactions between architectural components.

STILE is a graphical design and development environment. A system design is expressed by a set of blueprints . Each blueprint contains a set of graphical notations together with textural specifications to describe implementation details for each part of the system. STILE mainly focuses on description of the behavior of each system component and logical relationships among the components.

These ADLs and supporting tools address important issues of describing and analyzing system architecture with different concerns. However, these ADLs and tools (except STILE) are style-based in common. They try to give formal syntax and semantics to different architecture styles, which are frequently accompanied by box-and-line diagrams as the graphical notation. It is important to describe architecture styles as stated in [GaSh93,ShGa96,Shaw95a,Shaw95b,GAO94]; but it is not always clear that how subsystems interface and how they decompose. The graphical syntax produced by these ADLs and tools are complex, especially when the system is getting complex with multi-styles.UniCon and Wright attack the problem by providing decomposable components. But still, connectors with graphical ``lines'' are not decomposable. The jigsaw patterns technique facilitates this kind of abstraction.

If we carefully examine the examples given in this paper, it has already been illustrated that jigsaw patterns can also describe different architectural styles, e.g. pipes-filters , client-server , object-oriented , and Repository .

We have mentioned that jigsaw patterns alone does not provide information about details of the components, connectors and interfaces. The jigsaw patterns is designed as a decomposable substitute for box-and-line diagrams. Textual descriptions like ML or other ADLs are needed. It is possible to develop such an environment using jigsaw patterns on top levels, where each level can visualize the lower level decompositions by means of modern graphics tools. At a certain level, we can visualize the accompanying textual description for each component, connector and interface using ADLs or other modeling languages like e.g. UML (Unified Modeling Language) [Uml97].