Chapter 11. Conceptual Modeling of Processing Networks
For accommodating PN modeling, OEM-A is extended by adding pre-defined types for processing objects, entry node objects, arrival events, processing node objects, processing activities, exit objects and departure events, resulting in OEM-PN. These "built-in" types, which are described in Figure 11-1, allow making PN models based on them simply by making a process model (with DPMN) without the need of making an information/class model as its foundation, as shown in Figure 11-2.
An example of a conceptual PN model: Department of Motor Vehicles
As a simple example of a PN simulation model we consider a Department of Motor Vehicles (DMV) with two consecutive service desks: a reception desk and a case handling desk. When a customer arrives at the DMV, she first has to queue up at the reception desk where data for her case is recorded. The customer then goes to the waiting area and waits for being called by the case handling desk where her case will be processed. After completing the case handling, the customer leaves the DMV via the exit.
Customer arrivals are modeled with an «entry node» element (with name “DMV entry”), the two consecutive service desks are modeled with two «processing node» elements, and the departure of customers is modeled with an «exit node» element (with name “DMV exit”).
DPMN is extended by adding the new modeling elements of
- Entry/Processing/Exit Node rectangles representing node objects that take the form of stereotyped UML object rectangles;
- Processing Flow arrows representing the combination of an object flow arrow with an RDAS arrow (pointing to processing nodes), having a special arrow head consisting of a circle and three bars, as shown in Figure 11-2;
- Object-Event Flow arrows, representing the combined object-event flow from processing nodes to exit nodes, as shown in Figure 11-2.
Using both Processing Flow arrows and Event Flow arrows
While a Processing Flow arrow between two nodes implies both a flow of the processing object to the successor node and the resource-dependent scheduling of the next processing activity, an Event Flow arrow from a processing node to an Event circle represents an event flow where a processing activity end event causes/schedules another event, as illustrated in the example of Figure 11-3.
