# Transition Traversal Probabilities

The traversal of transitions for regular execution of process models is controlled
by the evaluation of transition conditions against possibly process data. To
evaluate transition conditions against data during simulation requires the generation
of data with appropriate assumptions about their value distribution. However,
to specify these assumptions especially for complex and structured data is very
challenging for the modeler.

Hence, the Simulation Feature allows you to simply provide probabilities
for the transition condition becoming true. It is assumed, that such probabilities
are reasonably easy to obtain based on some experience
with real world data ("What is the percentage of credit applications having
a total amount greater than $100,000").

*Note, that even if you decide to use the data
generation facility of the Simulation Feature, the generated data
are not correlated with the transition traversal probabilities.*

## Specifying Transition Traversal Probabilities

You can specify traversal probabilities in the **Simulation > Probability**
property page in the property dialog for outgoing activity gateways:

- In the
**Transition Settings** area select the transition.
- Now set the
**Maximum Traversal Count Per Process Instance**:
- Select the
**Distribution Type**. You have the choice between
`Gaussian`, `Poisson` and `Uniform`, which are described in detail in the chapter
Duration Probabilities.
- Enter the appropriate values.

### Controlling the Probability of Transitions in Case of Loops

Since it is possible to create a theoretically unlimited number of tokens from one process definition
(e.g. using AND-Splits), this should be avoided during simulation. Limiting the number of loop iterations is
possible using the **Maximum Transition Traversals Per Process Instance** configuration.
It allows to specify the maximum number of traversals one process instance can perform for a certain transition.
The default setting is `Poisson 10`.

### AND Split Gateways

For AND split gateways you may specify arbitrary percentages between
0 and 100% for each transition.

### XOR Split Gateways

For XOR split gateways the sum the traversal probabilities for
all transitions must be equal to 100.