Windows Workflow Foundation (WF) is an important Microsoft technology that was released as part of .NET 3.0 (originally called WinFX), which, along with Windows Communication Foundation (WCF) and Windows Presentation Foundation (WPF) layered on top of .NET 2.0. With .NET 4.0 these technologies are integrated into the .NET Framework. WF 4 is a major rewrite of this technology, offering significantly higher performance and making it easier to create and execute workflow applications. Visual Studio 2010 comes with a new visual designer built with WPF that supports the ability to work with much larger workflows. Learning WF can be challenging because it involves both new concepts and tools. An application is built using activities, which can be created with either procedural code in a language such as C# or Visual Basic or in XAML, the Extensible Application Markup Language that is also used in WPF. Typically workflows are created mainly in XAML using the visual designers in Visual Studio. There are three models for workflows: procedural, flowchart and state machine.