Split at exclusive gateway (XOR)
In an exclusive process pass, a token at a branch is only forwarded via one outgoing flow. The decision as to which branch is activated can be modeled in the BPMN process diagram using probabilities or events:
Probabilities
As soon as a token is activated at an exclusive gateway with multiple outgoing gates, a token with the process number of the activating token is forwarded via a gate. Forwarding is based on probabilities by default. Probabilities can be defined for outgoing sequence flows (Simulation attribute type group, Probability attribute). The sum of the probabilities of all sequence flows should be equal to 1.
If this is not the case, or if no probabilities have been specified, the following rules apply:
If all probabilities have been specified and they are equal to 0, nothing is changed.
If all probabilities have been specified and the sum is not equal to 1, the probability values are normalized so that their sum is equivalent to 1.
If probabilities have been specified only partly and their sum is less than 1, the difference between 1 and the sum of the specified probabilities is distributed equally among the probabilities that have not been specified.
If probabilities have been specified only partly and their sum is greater than 1, missing probabilities are set to 0 and the probabilities that have been specified are normalized so that their sum is equal to 1.
Events
An event-based exclusive gateway can be modeled by linking (Receive) tasks or intermediate events to it via sequence flows. A token arriving at a gateway waits until a message is received at one of the (Receive) tasks or until one of the events is triggered. As soon as this happens, a token is forwarded to the subsequent object via the corresponding sequence flow.