Division N

The coordination mechanism for this dependency consists of a place Pn with n tokens representing the available resources. This place is the input place for a transition connecting request_resource to assigned_resource, defining if there are available resouces. At the end of the task, the token returns to Pn via release_resource. Figure 28 shows the model for n = 3.

Figure 28: Coordination mechanism for division 3.

It is also possible that the resource be used by two different tasks, being requested by the first and released by the other that will eventually happen. This case is shown in Figure 29.


Figure 29: Coordination mechanism for division 3 with the resource being used by two conecutive tasks.

Figure 30 shows the mechanism using high level PN. The arcs with variable <x> ensure that the task that have requested the resource receives it. The insertion of another task that can also request the resource is made by connecting the new task to places request_resources, assigned_resources and release_resources.


Figure 30: Division n using high level PN.

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