In converting an object of one type to another, we expect some of the original object's behavior to remain the same and some to change. How can we state the relationship between the original object and converted object to characterize what information is preserved and what is lost after the conversion takes place? We answer this question by introducing the new relation, respects, and say that a type converter function C:A/spl rarr/B respects a type T. We formally define respects in terms of the Liskov and Wing behavioral notion of subtyping; types A and B are subtypes of T. We explain in detail the applicability of respectful type converters in the context of the Typed Object Model (TOM) Conversion Service, built at Carnegie Mellon and used on a daily basis throughout the world. We also briefly discuss how our respects relation addresses a similar question in two other contexts: type evolution and interoperability.

Many would argue that future breakthroughs in software productivity will depend on our ability to combine existing pieces of software to produce new applications.An important step towards this goal is the development of new techniques to detect and cope with mismatches in the assembled parts.Some problems of composition are due to low-level issues of interoperability, such as mismatches in programming languages or database schemas.However, in this paper we highlight a different, and in many ways more pervasive, class of problem: architectural mismatch.Specifically, we use our experience in building a family of software design environments from existing parts to illustrate a variety of types of mismatch that center around the assumptions a reusable part makes about the structure of the application in which is to appear.Based on this experience we show how an architectural view of the mismatch problem exposes some fundamental, thorny problems for software composition and suggests possible research avenues needed to solve them.

As the design of software architectures emerges as a discipline within software engineering, it will become increasingly important to support architectural description and analysis with tools and environments. In this paper we describe a system for developing architectural design environments that exploit architectural styles to guide software architects in producing specific systems. The primary contributions of this research are: (a) a generic object model for representing architectural designs; (b) the characterization of architectural styles as specializations of this object model; and (c) a toolkit for creating an open architectural design environment from a description of a specific architectural style. We use our experience in implementing these concepts to illustrate how style-oriented architectural design raises new challenges for software support environments.