Datasheet

Windows Workflow Foundation
Last but certainly not least, Windows Workflow Foundation rounds out the .NET Framework 3.0 platform
and is the main topic of discussion in this book.
Why Windows Workflow Foundation?
After reviewing all this information about workflows and process-oriented software, you might be won-
dering why Windows Workflow Foundation matters. The following paragraphs relate Windows Workflow
Foundation to the four tenets of workflow discussed earlier. This should help you determine whether to
use Windows Workflow Foundation in your software development efforts.
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This tenet is a key piece of
a workflow platform, and Windows Workflow Foundation provides several features that can
help you achieve this goal. Workflows built on this framework allow human interaction with
basically any interface imaginable — e-mail, web forms, windows forms, instant messaging,
InfoPath — the list goes on and on.
The important thing to remember is that the workflow realizes when it is requesting feedback
and waits until the required data has been received into the context of the application before
progressing. With the Windows Workflow Foundation platform, the possibilities are limited
only by your imagination.
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Windows Workflow Foundation provides a rich
framework of runtime services. These services, which are discussed in detail in Chapter 7, offer
you an extensible framework to, among other things, persist running workflows to a durable
medium. This is important because workflows can run for long periods of time, and storing a
workflow’s context in live memory isn’t practical for many reasons.
If every running workflow in an enterprise had to be stored in memory while waiting for some-
thing to happen, the scalability of the system would be nonexistent. The server would run out of
memory in no time. In addition, if the server crashed, the volatile memory would be cleared and
all data would be lost.
Workflows need to be reliably stateful. Out of the box, Windows Workflow Foundation provides
a way for you to persist a workflow’s state to a stable channel such as a database. You can extend
these persistence services to store workflow state just about anywhere.
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This is a large part of Windows Workflow
Foundation — just about every part of the platform is extensible. Workflows are made up of
discrete actions called
activities. Windows Workflow Foundation provides base activities as
well as basic and generic workflow functions. You can extend these activities to meet the needs
of essentially any requirement. You can also develop new activities from scratch.
There are many other parts of the platform that are extensible as well. Runtime services provide
functionality related to tracking, management, and persistence— which are all extensible.
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Windows Workflow
Foundation meets this requirement in two areas: design time and runtime. Because Windows
Workflow Foundation is based on a declarative and visual design-time model, processes are
easier to understand. This means you can modify existing workflows without having to change
source code.
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Chapter 1: An Introduction to Workflow and Windows Workflow Foundation
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