Algorithms for Managing the Evolution of Software Designs

Most software systems evolve, with time, in response to changing functional and non-function requirements. This evolution aaects both the dynamic behavior of the system as well as the form of the static software ar-tifacts (e.g., source code, user documentation, requirements speciications, design diagrams, test scripts) that comprise the system. A major challenge facing software practitioners is being able to evolve software artifacts to support new system features without corrupting these artifacts. For example, some questions that may arise during the design evolution process are: How does the introduction of a new module or subsystem aaect the structure of a software design? Does the addition of such components violate any constraints imposed by the design no-tation? Can the design be \repaired" automatically, if necessary, to satisfy the design constraints? Have any redundant components or relations been added by mis-take? Adding new features, or changing existing ones, is likely to involve a reconnguration of several entities and relations in a design diagram. In this paper we focus on how to evolve formal design diagrams in response to changing system requirements. By formal, we mean diagrams whose set of legal (well-formed) conngurations of entities and relations is determined by the syntax and semantics of the design notation. Our approach to managing the evolution of formal designs is based on a set of algorithms that facilitates the incremen-tal modiication of designs without compromising their well-formedness.