3. Activity Execution

BECAUSE A WF PROGRAM IS JUST an activity (that typically is the root of a tree of activities), the best way to understand how large WF programs execute is to first understand what happens at the level of a single activity.

The WF programming model codifies the lifecycle of an activity in terms of a finite state machine that we will call the activity automaton. Chapter 1, “Deconstructing WF,” introduced a simple three-state version of this automaton for resumable program statements. The lifecycle of activities also follows this basic pattern but adds several additional states that will be discussed in this chapter and the next.

The execution model for activities is fundamentally asynchronous because it is designed to accommodate ...

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