Architecture-Based Specification-Time Software Evolution

Software architectures shift the focus of developers from lines-of-code to coarser-grained architectural elements and their overall interconnection structure. Architectures have the potential to substantially improve the development and evolution of large, complex, multi-lingual, multiplatform, long-running systems. In order to achieve this potential, specific architecture-based modeling, analysis, and evolution techniques must be provided. To date, software architecture research has produced an abundance of techniques for architecture modeling and analysis, while largely neglecting architecture-based evolution. This dissertation motivates, presents, and validates a methodology for software evolution at architecture specification-time. The methodology consists of a collection of techniques that, individually and in concert, support flexible, systematic evolution of software architectures in a manner that preserves the desired architectural relationships and properties. The methodology is comprehensive in its scope: it addresses the evolution of individual architectural building blocks—components and connectors—as well as entire architectures; it also supports the transfer of (evolved) architecture-level decisions into implemented systems. The unique aspects of the methodology are: component evolution via heterogeneous subtyping, well suited to a wide rang