OASIS defines SOA as:
"A paradigm for organizing and utilizing distributed capabilities that may be under the control of different ownership domains. It provides a uniform means to offer, discover, interact with and use capabilities to produce desired effects consistent with measurable preconditions and expectations." (See OASIS-Open.org)
Other definitions also emphasise both the business aspects of the approach, and the fact that services encapsulate functionality, avoiding exposing the implementation:
"Service Oriented Architecture (SOA) is an architectural style that guides all aspects of creating and using business processes, packaged as services, throughout their lifecycle, as well as defining and provisioning the IT infrastructure that allows different applications to exchange data and participate in business processes regardless of the operating systems or programming languages underlying those applications." (See Newcomer, Eric; Lomow, Greg (2005). Understanding SOA with Web Services. Addison Wesley. ISBN 0-321-18086-0)
Others also emphasise its influence in encouraging organisations to create a set of "building-blocks" that can be connected to build applications:
"SOA represents a model in which functionality is decomposed into small, distinct units (services), which can be distributed over a network and can be combined together and reused to create business applications." (See Erl, Thomas (2005). Service-Oriented Architecture: Concepts, Technology, and Design. Upper Saddle River: Prentice Hall PTR. ISBN 0-13-185858-0.)