Common Principles of SOA

Service oriented architecture has some common principles which include:

1. Services are reusable:Service offered by one web service provider can be reuse in a WebApp or another web service.Web services are loosely coupled components which accelerates reuse.
2. Service share a formal contract:For the services to interact they need to share a formal contract,that include:formal definition of service end point,each service operation,every input and output msg supported by each operation,rules and characteristics of the service and its operation.
3. Services are loosely coupled:Services must be designed to interact with other application or web service without tigh coupling or any type of dependency.
4. Service abstract the underlying logic:The service abstract the underlying logic of its implementation but provide access to its functionality or operation through interfaces.
5. Services are composable:The service may compose other service.
6. Services are autonomous:The service s reside inside a well defined boundary and for the successful execution of  a service it does not depend on other service.
7. Services are stateless:Service are not allowed to store the state information as it will not allow the service to be loosely coupled.
8. Service are discoverable:The service should allow thwer description to be searched and understood by humans.