Technical basics-Windows worldflow Foundation

Translated to understanding WF in WSS and Office 2007 v1.doc
Author: David Chappell, Chappell & Associates)

See: http://www.davidchappell.com/blog/index.html for full text

In software implementation, it is often necessary to include a defined multi-step flow process. If there are many Program So why not directly provide a software that contains such an application? Windows worldflow foundation is created for this purpose. A wf-based application is composed of multiple workflows. Each workflow contains many activities ). each activity is executed on the WF running engine at a certain time in the workflow position. In process-oriented programs, WF makes them easier to create and maintain.
The following figure shows the main components of WF. A workflow consists of multiple activities and runs on the runtime engine. The execution process depends on the lower-layer runtime services ). The service tracks the workflow status and execution process. It can host a desktop program or a large server. It can adapt to various environments. When necessary, runtime services can be replaced in various environments.
WF can be visually designed in Visual Studio. You can create various workflows and drag them to create them. An activity is a class, so it is entirely possible for you Code Activities. A workflow can be composed of any activity, including the BAL (base activity Library) provided by WF, or an activity created by itself. Bal contains some common and basic activities:
> Ifelse: there are two or more optional Paths Based on the conditions.
> While: repeats one or more activities.
> Sequence: specify an activity group in sequence.
> Parallet: Two or more groups of activities are executed simultaneously.
> Code: execute a defined code snippet.
> Listen: listens to the event set. when an event occurs, the activity is triggered.
> Invokewebservice: Reference WebService.
> Policy: Use the Rules Engine provided by WF to define and execute business logic.
WF provides two built-in workflows:
> Sequential workflows: A series of activities defined for execution. It can contain ifelse, while, and other activities.
> State machine workflows: executes a traditional finite state machine that can contain ifelse, while, and other activities. It is switched from the status of other activities.

It is important to understand that WF is not a workflow application, but to provide a foundation for developing workflow applications. It can host in any windows application or provide workflow services in combination with other technologies. Wwsv3 is a good example.