An architectural decision modeling framework for service-oriented architecture design

Enterprises in numerous industries rely on Information Technology (IT) solutions today; enterprise applications support and partially automate the execution of the business processes in these enterprises. It is challenging to develop and integrate such enterprise applications, which can be characterized as logically layered and physically distributed software systems. In recent years, Service-Oriented Architecture (SOA) concepts have matured into an important architectural style for enterprise application development and integration. From a usage perspective, a key principle in SOA is the business alignment of services. From an architectural perspective, SOA principles include modularity, loose coupling (i.e., platform, location, protocol, and format transparency), as well as logical layering and flow independence. Key SOA patterns are service consumer-provider contract, Enterprise Service Bus (ESB), service composition, and service registry. Service consumers and providers as well as ESB and service composition infrastructure have to fulfill numerous Non-Functional Requirements (NFRs). Many NFRs concern software quality attributes in areas such as reliability, usability, efficiency, maintainability, and portability. Other NFRs result from enterprise architecture guidelines and constraints of legacy systems. Old and new challenges arise, e.g., interface contract design and serving a large number of heterogeneous service consumers. There are no straightforward answers to the resulting SOA design questions; design methods are required. Existing design methods provide many service identification and specification techniques; however, they do not cover service realization sufficiently. Project experience makes evident that there is more to realizing services of quality and style than identifying abstract services in functional requirements, specifying them with technical interface contracts such as Web Services Description Language (WSDL) port types, and applying WSDLto-code transformation wizards: Many architectural decisions are required. Architectural decision modeling is an emerging field in software architecture research. Unlike other architecture documentation approaches, architectural decision models capture the architectural knowledge justifying certain designs (rationale). Architectural decisions concern a software system as a whole, or one or more of the core components of such a system. Architectural decisions directly or indirectly determine the non-functional characteristics of a system, e.g., its software quality attributes. Each decision describes a concrete design issue which has several potential solutions (alternatives) that are chosen from. Examples are the selection of programming language and tools, of architectural patterns, of integration technologies, and of middleware assets.