Alternative

The Alternative relation is originally not defined by RST. We have defined the Procedural Semantics of this relation accordingly to the definition of other relations in RST and not using its behavior. Therefore, it is categorized as an RST Relation.
The nuclei of an Alternative relation represent alternative paths of the information flow. For the use in dialogs we have specified the relation as follows. By executing the relation, one of the nuclei has to be executed until its final state is reached. It is possible to start executing more than one nuclei, but only one can be finished. To specify which communication party selects the nucleus executed until its final state is reached, the communication party has to specified.
Figure Alternative shows the behavior as a state chart. In this state chart the nuclei states are inside the Alternative composite state. This allows that more than one nucleus can be executed at the same time. To model that only one nucleus can be executed until its
final state is reached, a transition from each nucleus state to the final state of the state chart exists.