Service Oriented Architecture

Question

What is Service oriented Architecture ?

Answer 1

WCF is a technology which makes building services easier, and it works on all transports not only HTTP so it is more generic than Web Services which works only on Http.

Answer 2

SOA is a way to design a complete solution, it is a set of commonly accepted practices for communication, state management, compatibility, etc. In software architecture specifically, SOA is a set of services (not necessarily Web Services) that are built independently to support a range of client applications. The modular design helps maintenance, business collaboration. SOA also provides some guidelines for development:

• Constraints over backward compatibility
• Metadata exposure
• Discoverability of services

On the other hand, WCF is just a supporting technology that helps you build the services in .NET.

You can create a SOA without WCF, just as creating a bunch of WCF services does not make your architecture a service oriented one.

Answer 3

SOA is way to develop service oriented applications and WCF is technology which can be used to develop service oriented applications. BUT SOA defines strict rules (known as SOA tenets) for applications. If you don't follow these rules you are building services but these services do not conform to SOA.

WCF allows you to develop plenty of types of services. You can develop interoperable SOAP services which conform to SOA or which doesn't. You can develop pure .NET services with non interoperable features and you can develop REST services.

Moreover in SOA service can have different meaning than in WCF. In WCF service is collection of functionality exposed on endpoints. In SOA the service can be whole application (set of WCF like services) - difference between small and big SOA.

SOA tenets are:

• Boundaries are explicit - service doesn't share anything with other services (even database tables and data can't be shared)
• Services are autonomous - each service is independent, can be separately deployed and versioned
• Services share schema and contract, not class - services are described in WSDL, transported data are described in XSD, orchestrations (aggregation) are described in BPEL
• Services compatibility is based upon policy - WSDL contains WS-Policies to describe configuration needed for interoperability

As you see especially first two tenets can be easily violated when building WCF service.