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Services are reusable
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Service-orientation encourages reuse in all services, regardless if immediate requirements for reuse exist. By applying design standards that make each service potentially reusable, the chances of being able to accommodate future requirements with less development effort are increased. Inherently reusable services also reduce the need for creating wrapper services that expose a generic interface over top of less reusable services.
This principle facilitates all forms of reuse, including inter-application interoperability, composition, and the creation of cross-cutting or utility services. Because a service is simply a collection of related operations, it is therefore the logic encapsulated by the individual operations that must be deemed reusable in order to warrant representation as a reusable service.
 A reusable service exposes reusable operations.
Messaging also indirectly supports service reusability through the use of SOAP headers. These allow for messages to become increasingly self-reliant by grouping metadata details with message content into a single package (the SOAP envelope). Messages can be equipped with processing instructions and business rules that allow them to dictate to recipient services how they should be processed.
The processing-specific logic embedded in a message alleviates the need for a service to contain this logic. More importantly, it imposes a requirement that service operations become less activity-specific � in other words, more generic. The more generic a service�s operations are, the more reusable the service.
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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