A formal basis for architectural connection

Reviewer: Markus Wolf

Allen and Garlan present a formal approach to the description of the architectural design of interacting components of a software system. The intention of the approach is to extend traditional methods of formalizing architectural design (Interface Definition Languages and Module Interconnection Languages) to handle the interaction between communicating components. In the first few sections, this motivation is discussed extensively. These sections also distinguish between the common focus of design descriptions, which are based on hierarchical definition/use principles, and the needs of interactive systems, where the components act independently at the same hierarchical level. After a short discussion of the requirements that the authors expect a suitable formalism for interactive systems to fulfill, they describe the particular approach they have chosen and have embedded in an architectural description language called WRIGHT. The language divides a system into components and connectors, where the connectors serve as an abstraction of the interaction behavior of the system. The connectors consist of roles describing the expected local behavior of interacting components and a “glue” specification determining their interaction obligations. These concepts are illustrated by examples. A notation derived from CSP is used to describe roles and glues. CSP is also used as a semantic foundation for the language. Using CSP as a semantic foundation enables the authors to use existing analysis tools to prove such properties as deadlock freedom and compatibility of components. These technical issues are discussed extensively in the later sections. The paper finishes with a discussion of the design decisions of the proposed formalism. The paper explains the formalisms and concepts in clear, crisp language, and I could find only one typo (in Definition 10.2, P should be replaced by S ). At first sight, the discussions seem to be overly long, but the topic is relatively new, and a proper justification seems to be helpful.