The core principles of an SOA

So what exactly is a service? A service is essentially a well-defined interface to an autonomous chunk of functionality, which usually corresponds to a specific business process. That might sound a lot like a regular old object-oriented component to you. While both services and components have commonality in that they expose discrete interfaces of functionality, a service is more focused on the capabilities offered than the packaging. Services are meant to be higher-level, business-oriented offerings that provide technology abstraction and interoperability within a multipurpose "services" tier of your architecture.

What makes up a service? Typically you'll find:

• Contract: Explains what operations the service exposes, types of messages, and exchange patterns supported by this service, and any policies that explain how this service is used.

• Messages: The data payload exchanged between the service consumer and provider.

• Implementation: The portion of the service...