Sunday, January 31, 2010

SOA - Service Orientation

1. What is SOA ?
a, An SOA consists of a set of resources on a network that are made available as independent services , and that can be accessed without required any knowledge of how they are implemented.
b, We can combine the services in an SOA to create an enterprise application.

2. What are the benefits of SOA ?
Ans: It enables you to create complex solutions that are independent of any specific platform. and location. that is you can quickly replace or upgrade a service or move a service to a different site. and as long as the service exposes the same interfaces as before, you can continue to use it without needing to modify any code.

3. What are the 4 tenets of Service Orientation which are required to solve the Distributed application architecture problems and to successfully design and implement an SOA?
1. Boundaries are Explicit: We should not make any assumptions about how a service processes a request or how a client application handles any response to a request . Following this principle removes any dependencies between the client and service applications.
2. Services are autonomous: We should design our solutions to be loosely coupled, so that they can tolerate the changes (Location of a service might change, or service might be taken offline for maintenance purposes or for other reasons). and continue running even if one or more services are unavailable.
3. Services share schemas and contracts, not classes or types. If you need to modify a service and provide additional functionality, you can add contracts and schemas that extend the original capabilities of the service while retaining the existing contracts and schemas. Older client applications should continue to work unchanged.
4. Compatibility is based on policy: You should design services so that their policy requirements are independent of any implementation, and you should enforce clients to abide by any policies required by the service. Additionally, all services and client applications must agree on how to specify this policy information (typically by using some sort of configuration file). This is the purpose of the WS-Policy framework.

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