Architecture of Windows Workflow Foundation

WF itself is a programming model, along with an engine and a set of tools for building workflowenabled applications. The programming model is made up of exposed APIs that other programming languages can use to interact with the workflow engine. These APIs are encapsulated within a namespace called System.Workflow. That namespace will be part of the WinFX programming model, but can also be installed as an add-on to the existing .NET Framework 2.0.