Windows Workflow Foundation

Windows Workflow Foundation (WF) is a Microsoft technology for defining, executing, and managing workflows. This technology is part of .NET Framework 3.0 which is available natively in the Windows Vista operating system, and can be installed on the Windows XP SP2 and Windows 2003 Server operating systems.

Authoring Workflows

A new XML-based language XAML is commonly used for declaring the structure of a workflow. However, the workflow may also be expressed in code using any .NET-targeted language (VB.NET, C#, C++/CLI, etc.).

Workflows comprise 'activities'. Developers can write their own domain-specific activities and then use them in workflows. WF also provides a set of general-purpose 'activities' that cover several control flow constructs.

Windows Workflow Foundation is supported by a companion set of extensions to Visual Studio 2005. These extensions contain a visual workflow designer which allows users to design workflows, a visual debugger which enables the users to debug the workflow designed, and a project system which enables the user to compile their workflows inside Visual Studio 2005.

Moving data through Workflows

Activities that require or provide data can use properties to expose them, and enable the Workflow author to bind them to the containing workflow by declaring 'dependencies'.

Hosting Workflows

The .NET Framework 3.0 "workflow runtime" provides common facilities for running and managing the workflows and can be hosted in any CLR application domain, be it a Windows Service, a Console, GUI or Web Application.

The host can provide services like serialization for the runtime to use when needed. It can also hook up to workflow instance's events such as their becoming idle or stopping.

Communicating with Workflows

WF workflows define interfaces with methods and events to communicate with the outside world. A host application typically sets up an environment before running a workflow, providing objects that implement those interfaces.

When an object implementing such interfaces raises an event, the corresponding workflow is retrieved and the data passed on to it.

Methods on the interface may be used by the workflow to communicate with its host.