http://blogs.msdn.com/b/innov8showcase/archive/2010/02/01/a-look-at-the-workflow-foundation-4-0-activity-model.aspxWorkflow Activity Model Windows Workflow Foundation (WF) in .NET Framework version 4 changes several development paradigms from previous versions; Workflows are now easier to create, execute, and maintain, and implement a host of new functionality. Theen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)