How do I do this? A lot of times people get stuck with the impression that there are only two workflow models available: sequential and state machine. True, out of the box these are the two that are built in, but only because there are is a set of common problems that map nicely into their execution semantics. As a result of these two being "in the box," I often see people doing a lot of very unnatural things in order to fit their problem into a certain model. The drawing above illustrates the flow of one such pattern. In this case, the customer wanted parallel execution with two branches ((1,3) and (2,5)). But, they had an additional factor that played in here, 4 could execute, but it could only execute when both 1 and 2 had completed. 4 didn't need to wait for 3 and 5 to finish, 3 and 5 could take a long period of time, so 4 could at least start once 1 and 2 were completed. Before we dive into a more simple solution, let's look at some of the ways they tried to solve the problem, in an attempt to use "what's in the box." The "While-polling" approach The basic idea behind this approach is that we will use a parallel activity, and in the third branch we will place a while loop that loops on the condition of "if activity x is done" with a brief delay activity in there so that we are not busy polling. What's the downside to this approach: The model is unnatural, and gets more awkward given the complexity of the process (what do we do if activity 7 has a dependency on 4 and 5) The
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