Service-Oriented Architecture - For the purpose of this Instruction, a paradigm for defining, organizing, and using distributed capabilities in the form of loosely coupled software services 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 that are consistent with measurable preconditions and expectations. E2.55.
NIST SP 800-95
Service-Oriented Architecture (SOA) - A collection of services. These services communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity. (Open Grid Services Architecture Glossary of Terms (25 January 2005), http://www.gridforum.org/documents/GFD.44.pdf)