R9

R9 / 1:Mc

Action Type is injected or monitored in zero, one or many Interaction

Interaction injects or monitors exactly one Action Type

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By definition, an Interaction is a point in a Scenario where some Action Type is injected as a System Input or observed as a System Output.

The same Action Type can happen at multiple times in a Scenario.

Since Action Types are defined for a Modeling Language and are used across Systems or System variations, it makes sense to just build up a catalog of all Action Types that are likely to be referenced. Consequently, some of them might not participate in an Interaction in a given Scenario.