Each transitions is written under the TRANSITION descriptor. A transition may have the following 5 properties. Some of them are optional.
The S property, the N property, and either the E property or the T property are obligatory for each transition. The value of the E property is the name of the event that triggers the transition. The value of the T property, which may be a Python expression to be evaluated at run-time, is the time (in seconds) to be scheduled in advance. It is equivalent to the event in the abstract syntax. A transition cannot have both E and T properties.
The properties of a transition are specified in separate lines after the TRANSITION descriptor. Their order is not important. For transitions that have multiple output actions, each action is written on a single line, and all those actions are left-aligned with 0 or more leading spaces. Similarly, more than one guard can be written in consecutive lines with left-alignment. Those guards have ``and'' relations. Alternatively, they can also be written in a single line with the and operator in the constraint language (Python) between them.
As an example, the model in Figure 4.7 is textually written as the textual representation in Table 4.5.
Timed transitions are a special kind of transitions that have the T property instead of E. An example of timed transition is shown in Table 4.6. This transition is triggered seconds after state A is entered. The transition is enabled after the scheduled time only if and .