· Windows Workflow Foundation (WF) is a programming model, engine and tools for defining, building, executing, debugging and managing workflows on Windows.
- WWF consists of namespace (System.Workflow), an in-process workflow engine, and designers for Microsoft Visual Studio 2005.
- Windows Workflow Foundation is a programming framework to build workflow enabled applications.
- System.Workflow.ComponentModel is the name space in which most of the abstractions used in WWF are defined.
· A workflow is a set of activities that are stored as a model.
- A workflow is a set of activities that are stored as a model.
- Workflow is nothing but a set of activities that are organized in a tree structure. Activities are the fundamental building blocks of workflows.
- Workflow instance is created and maintained by an in-process workflow runtime engine.
- The Workflow runtime engine is responsible for creating and maintaining running workflow instances.
· Core Components of WWF:
- Base Activity Library: Out-of-box activities which provides functionality for control flow, conditions, event handling, state management and invoking web service. One can build their own custom domain-specific activities using the base activity.
- Runtime Engine: Workflow execution and state management
- Runtime Services: Hosting flexibility and communication
- Visual Designer: Graphical and code-based construction
· Workflows run within a Host Process.
- Once a workflow model is compiled, it can be executed inside any Windows process including console applications, Windows Forms applications, Windows Services, ASP.NET Web sites, and Web services.
· Traditional programming languages won’t support program durability, persistence and long running process. Windows Workflow Foundation is flexible, extensible and supports long running process.
· Work Flow also separates business logic from the code. Developers can build their own custom activities and reuse the same.
· A workflow can be expressed in either declarative XAML or in imperative code using any .NET language like C# and VB.NET.
- You can build workflows directly in code, in markup, or in a combination of both. Pure XAML has an advantage of loading into memory with out compilation.
- Work flow application can be authored in three ways including Code-only (C# and VB.NET), Code-separation (XAML+ C#/VB.NET) and No-Code (XAML).
· Visual workflow designer to design workflows, a visual debugger to debug the workflow designed and project system to compile their workflows inside Visual Studio 2005.
· WWF supports three kind of workflows including sequential, state-based and data driven workflows involving both human and system interaction.
- Sequential workflow is a map of activities with a Start and an End, in series or parallel.
- We can use Sequential work flow, if activities are predictable and repeatable.
- State-based workflow is a state machine where events cause transitions.
- In data-driven workflow, activities are run based on a data state.
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