Service Oriented Architecture

SOA :
A service-oriented architecture is essentially a collection of services. These services communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity. Some means of connecting services to each other is needed.

Service:
A service is a function that is well-defined, self-contained, and does not depend on the context or state of other services

Orientation:
When we are building our systems we are looking at them from a service point of view or orientation. This implies that we are oriented or interested in the following:

• Granularity: The level of service interface or number of interactions required with the service, typically characterized as course grained or fine grained.
• Collaboration: Services may be combined together to create higher level or composite services.
• Universality: All components can be approached from a service perspective. For example, a business process may also be considered a service that, despite its complexity, provides inputs and outputs.

Architecture:
It implies a consistent and coherent design approach. This implies a need to understand the inter-relationships between components in the design and ensure consistency in approach. Architecture suggests that we adopt some of the following principles:

Consistency: The same challenges should be addressed in a uniform way.For example, the application of security constraints needs to be enforced inthe same way across the design. Patterns or proven design approaches can assist with maintaining consistency of design

Reliability: The structures created must be fit to purpose and meet the
demands for which they are designed.

Extensibility: A design must provide a framework that can be expanded in ways both foreseen and unforeseen. See the break out box on extensions.