Interoperability Using Windows Communication Foundation (WCF)

The Windows Communication Foundation (WCF), formerly known as Indigo, is the long-term solution from Microsoft for connected systems. It provides APIs that subsume Web services, remoting, messaging and all other connectivities. It is built around Web services architecture and is designed to provide secure, reliable, and transacted messaging along with interoperabilitybased on open standards. It is intended to span across multiple transports, security systems, messaging patterns, encodings, network topologies, and hosting models. It will be at the core of the upcoming Windows Vista (formerly Longhorn) series as well as have backward support for Windows XP and Windows Server 2003. Due for release in 2006, WCF is intended to interoperate cleanly with all systems (including Java EE systems), but as it evolves it is worth monitoring over time to prove out its adherence to standards before the decision is made to use or deploy it in a diverse system.

• Declarative Programming In declarative programming, developers define specific attributes and interfaces, which are the key "data contract" between service requesters and service providers. In WCF, "service contracts" are used to specify session requirements and service operation direction using parameters.

• Imperative Programming Using data object models derived from the application programming interfaces provided by WCF, developers can use object-oriented programming to create and access services or extend existing services easily. In WCF, developers can also define "channels" to support a different transport or protocol. WCF channels connect the service model layer with the actual data on the wire. There are two different types of WCF channels: transport channels (responsible for sending and receiving data) and protocol channels (that implement specific message exchange protocols). This provides flexibility and extensibility for WCF applications to integrate and interoperate with different platforms (such as Java EE applications) that use different messaging protocols.

• Configuration-Based Programming Developers can specify part of an application's behavior (such as addresses, bindings, security details, or service behavior) in configuration files. This allows the runtime to make deploy-time decisions about services without rewriting the application codes.

WCF is fairly complex and is still evolving before the final release. It is much more powerful in its interoperability features than WSE or other .NET technologies. For example, WCF supports MTOM, Metadata Exchange or MEX, and SAML 1.1. These are fairly significant interoperability features. From an interoperability perspective, it is important to understand that it provides flexible programming approaches to build services and interacts (and interoperates) with Web services implemented in different protocols and technologies. The table below ummarizes the .NET interoperability capabilities of ASMX, WSE, and WCF