Introduction
 About this Site
 About the Principles

Common Principles of Service-Orientation
 Service reusability
 Service contract
 Service loose coupling
 Service abstraction
 Service composability
 Service autonomy
 Service statelessness
 Service discoverability

How Service-Orientation Principles Inter-relate
 Service reusability
 Service contract
 Service loose coupling
 Service abstraction
 Service composability
 Service autonomy
 Service statelessness
 Service discoverability

Service-Orientation and Related Principles and Paradigms
 Separation of Concerns
 Object-Orientation (Part I)
 Object-Orientation (Part II)
 Object-Orientation (Part III)

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   Service-Orientation
 About the author
Service-orientation and Object-orientation (Part I)
Those of you familiar with object-oriented (OO) analysis and design will recognize a similarity between a number of the service-orientation principles and the more established principles of object-orientation. Indeed, service-orientation owes much of its existence to object-oriented concepts and theory. Below we provide a look at which common object-orientation principles are related to the service-orientation principles we�ve been discussing.

Service reusability

Much of OO is geared toward the creation of reusable classes. The OO principle of modularity standardized decomposition as a means of application design. Related principles, such as abstraction and encapsulation, further support reuse by requiring a distinct separation of interface and implementation logic. Service reusability is therefore a continuation of this OO goal.

Service contract

The requirement for a service contract is very comparable to the use of interfaces when building object-oriented applications. Much like WSDL definitions, interfaces provide a means of abstracting the description of a class. And, much like the �WSDL first� approach encouraged within SOA, the �interface first� approach is also considered an OO best practice.

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.
Opinions

"The notion that boundaries are explicit applies not only to inter-service communication but also to inter-developer communication.

Even in scenarios in which all services are deployed in a single location, it is commonplace for the developers of each service to be spread across geographical, cultural, and/or organizational boundaries.

Each of these boundaries increases the cost of communication between developers. Service orientation adapts to this model by reducing the number and complexity of abstractions that must be shared across service boundaries."


- Don Box, Microsoft






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