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354 G. Decket et al.
more Trackpoints
Carrier Trackpoint
Issue
Notice

Carrier Admin Officer Log Trackpoint
Order Entry

Fig. 13.5 Example of a business process model with lanes

Clearly, BPMN is rather limited when it comes to representing resources. Many
of the constructs that are possible in YAWL are not possible in BPMN. Examples
of constructs for which YAWL has specific support, but BPMN does not, include
the following: representing that a resource can delegate a task to another resource;
representing that a check must be performed by another individual than the individ-
ual who performed the previous task (the “separation of duties” resource pattern);
and representing that a task should be performed by the individual who has done the
most of these tasks in the past.
Figure 13.5 shows an extension of the example from Fig. 13.1, in which lanes
have been added to represent the roles that are authorized to perform tasks. It
shows that the Carrier is authorized to perform Issue Trackpoint Notice and that
the Carrier Admin Officer is authorized to perform Log Trackpoint Order Entry.

13.2.4 Exceptions

BPMN supports exceptions by allowing intermediate events to be attached to tasks
and subprocesses. An intermediate event is attached to a task or a subprocess repre-
sents that the task or the subprocess (and everything in it) can be interrupted by the
occurrence of the intermediate event. Upon occurrence of the intermediate event, the
task or subprocess stops executing and the flow continues along the sequence flow
that leaves the intermediate event. The “type” of the intermediate event specifies
what kind of exception it reacts to. The timer, message, error, and rule intermediate
events discussed previously can be attached to tasks and subprocesses to repre-
sent an exception. An error event on a subprocess can have a counterpart (an error
event with the same name) in that subprocess. When this is the case, the error event
“catches” the error when it is “thrown” in the subprocess.
In addition to these types, “cancel” and “compensate” events can be attached
to tasks and subprocesses. These events correspond to cancelation and compen-
sation of transactions. However, in BPMN 1.0, their semantics is underspecified.
Therefore, we do not discuss them here.