The primary objective of service-oriented architecture (SOA) is to use information technology to address the key goals of business today: innovation, agility, and market value. Agility in SOA is achieved by use of the principles of encapsulation, modularity, and loose coupling, which facilitates a cleaner separation of concerns. While loose coupling enables customers to rapidly reuse services in new applications, strong coherency must be maintained to achieve the primary business objectives of the application. When applications are composed of loosely coupled services that are independent (owned by different parts of the organization, based on disparate technology assumptions, and evolving on independent schedules and with diverse priorities) the coherency of the composite application can be undermined. In this paper, we examine how coherency can be created and maintained in loosely coupled applications. We examine, in this context, various techniques and design approaches, such as service management, the use of service buses, the role of industry models and semantic ontologies, and governance, to achieve and maintain coherency of composite applications using SOA.
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