This data module represents the resources of the system that can be used to process entities. Each resource has a number of available units (Capacity), and if no idle units are available an entity will have to wait before being processed.
The resource element can receive seize petitions from one or more Process modules (through port S). If the required number of units is idle, the entity seizes the resource and a confirmation (ACK) is sent to the Process module (indicating that the entity can continue). If no enough resource units are available, the petition will wait in a FIFO queue until some resources are released.
This element also can receive release petitions (through port R). These petitions increase the number of idle resource units and check if any seize petition in the queue can be satisfied.