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Service contract and other principles
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 The service contract and its relationship with
other service-orientation principles.
A service contract is a representation of a service�s collective metadata. It standardizes the expression of rules and conditions that need to be fulfilled by any requestor wanting to interact with the service.
Service contracts represent a cornerstone principle in service-orientation, and therefore support other principles in various ways, as follows:
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Service abstraction is realized through a service contract, as it is the metadata expressed in the contract that defines the only information made available to service requestors. All additional design, processing, and implementation details are hidden behind this contract.
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Service loose coupling is made possible through the use of service contracts. Services do not need to be bound together or dependent on each other; they simply need an awareness of each other�s communication requirements, as expressed by the service description documents that comprise the service contract.
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Service composability is indirectly enabled through the use of service contracts. It is via the contract that a controller service enlists and uses services that act as composition members.
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Service discoverability is based on the use of service contracts. While some registries provide information supplemental to that expressed through the contract, it is the service description documents that are primarily searched for in the service discovery process.
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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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