Java Reference
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Applications
“Rest, the sweet sauce of labor.”
—Plutarch
Service-oriented architecture (SOA) and development is a paradigm where soft-
ware components are created with concise interfaces, whereby each component
performs a discrete set of related functions. Each component, with its well-
defined interface and contract for usage, can be described as providing a service
to other software components. This is analogous to an accountant who provides a
service to a business, even though that service consists of many related functions
(i.e., bookkeeping, tax filing, investment management, and so on).
With SOA, there are no technology requirements or restrictions. You can build a
service in any language with standards such as CORBA, platform-specific
remote procedure calls (RPC), or the more universally accepted XML. Although
SOA has been around as a concept for many years, its vague definition makes it
difficult to identify or standardize upon. The client/server development model of
the early 90s was a simple example of an SOA-based approach to software
development.
A Web service is an example of an SOA with a well-defined set of implementa-
tion choices. In general, the technology choices are the Simple Object Access
Protocol (SOAP) and the Web Service Definition Language (WSDL), both
XML-based. WSDL describes the interface (also called the contract), whereas
SOAP describes the data that is transferred. Because of the platform-neutral
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