In order for large, complex, multi-lingual, multi-platform, long-running systems to be economically viable, they need to be evolvable. Support for software evolution includes techniques and tools that aid interchange, reconfiguration, extension, and scaling of software modules and/or systems. Evolution in the current economic context also requires support for reuse of third-party components. The costs of system maintenance (i.e., evolution) are as high as 60 percent of the overall development costs. Practitioners have traditionally faced many problems with curbing these costs. The problems are often the result of poor understanding of a system’s overall architecture, unintended and complex dependencies among its components, decisions that are made prematurely in the development process, and so forth. Traditional development approaches (e.g., structural programming or object-oriented analysis and design) have in particular failed to properly decouple computation (performed by components) from communication (facilitated by connectors) within a system, thus supporting only limited reconfigurability and reuse. Evolution techniques have also typically been programming language specific (e.g., inheritance) and applicable on the small scale (e.g., separation of concerns or isolation of change). This is only partially adequate in the case of development with preexisting, large, multi-lingual, multi-platform components that originate from multiple sources.

In this talk, Medvidovic will posit that an explicit architectural focus can remedy many of these difficulties and enable flexible construction and evolution of large systems. In particular, the talk focuses on two techniques that can aid architecture-based development and evolution: heterogeneous typing and explicit software connectors. The two techniques will be presented and their benefits demonstrated in the context of a specific architectural style. More general applicability of the techniques will be discussed.