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Service composability and other principles
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 Service composability and its relationship with
other service-orientation principles.
Designing services so that they support composition by others is fundamental to building service-oriented solutions. Service composability therefore is tied to service-orientation principles that support the concept of service composition, as explained below:
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Service reusability is what enables one service to be composed by numerous others. It is expected that reusable services can be incorporated within different compositions as well as reused independently by other service requestors.
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Service loose coupling establishes a communications framework that supports the concept of dynamic service composition. Because services are freed from many dependencies, they are more available to be reused via composition.
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Service statelessness supports service composability, especially in larger compositions. A service composition is reliant on the design quality and commonality of its collective parts. If all services are stateless (by, for example, deferring activity-specific logic to messages), the overall composition executes more harmoniously.
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Service autonomy held by composition members strengthens the overall composition, but the autonomy of the controller service itself is actually decreased due to the dependencies on its composition members.
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Service contracts enable service composition by formalizing the runtime agreement between composition members.
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This page contains excerpts from:
Service-Oriented Architecture:
Concepts, Technology, and Design
by Thomas Erl
(ISBN: 0131858580, Prentice Hall/PearsonPTR, Hardcover, 792 pages).
For more information, visit www.soabooks.com.
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