Where are We?

Chapters 3 and 4 together have presented the complete activity automaton, and the details of the execution model for activities. This asynchronous execution model rests firmly on the ideas of bookmarks and continuations, and goes hand in hand with the episodic execution of WF programs. The embodiment of the WF execution model is the activity automaton, along with a set of constraints, enforced by the WF runtime, that govern the runtime relationships between any composite activity and its child activities.

Because all WF programs are just compositions of activities, we have also come to see how, viewed from the inside, an in-memory WF program instance is a set of CLR objects, which transiently represent activities within various execution contexts.

In the next chapter, we will shift our perspective and take a look at WF programs from the outsidethat is, from the vantage point of the application that hosts the WF runtime and manages the execution of WF program instances.