Towards Evolution Methodology for Service-Oriented Systems

Modern organisations are forced to evolve their IT systems to keep up with ever-changing business requirements. Service-Oriented Architecture addresses the challenge of boosting a system's modifiability by composing a new functionality out of existing, independent, loosely-coupled services. This makes SOA a promising design paradigm for rapidly evolving systems. However, existing development methodologies for SOA, such as IBM's SOMA, focus more on the transition from legacy non-SOA to SOA systems, and less on their subsequent evolution. This makes the development of an evolution methodology suitable for service-oriented systems an open research problem. The presented evolution methodology comprises an evolution process and an evolution documentation model. The process is compliant with a popular ISO 20000 norm. Its artefacts have been defined in terms of the evolution documentation model. The business-driven changes are documented with architectural decisions that capture changes made to the system at various levels of scope, together with their motivation. In order to facilitate the change-making process, a set of typical change scenarios has been defined. It comprises typical sequences of architectural decisions for cases of the most important changes. The entire approach is illustrated with a real-world example of an internet payment system.