Principles of Service-Oriented Architectures

In service-oriented architectures (SOAs), key applications all have Web services front ends that enable them to communicate with other applications using XML-formatted messages, typically over standard Internet protocols. SOAs aim for a level of application integration that has so far proven elusive, despite the best efforts of vendors such as IBM and Microsoft. The goal of application integration is to reduce business transaction times and errors by automating the process of transferring information among systems, and to improve IT efficiency by allowing business logic (for example, inventory processing and control rules) to be hosted in a single application and then accessed from other applications.

To respond to these needs, vendors introduced a number of distributed object technologies, such as the Distributed Component Object Model (DCOM) developed by Microsoft, and the Common Object Request Broker Architecture (CORBA) developed by IBM along with smaller vendors such as Iona. DCOM and CORBA both started with the assumption that the same technology used to integrate components within an application could be stretched to integrate among applications. They allowed components within one application to invoke components in another application. But they failed to take into account what has since become a key tenet of SOAs: boundaries matter.