R5

R5 / M:Mc-M

Actor participates in zero, one or many Interaction

Interaction involves one or many Actor

---

The same Actor can participate in any number of Interactions, each in a potentially different Role.

The UI Actor (domain), for example, could be the initiator of one Interaction and be the target of yet another.

And it is even possible for the same Actor to play more than one Role in the same Interaction, hence the many associative multiplicity. (no example comes to mind, but it makes sense in principle)

A Role is, by definition, the usage of some Actor in the context of a Interaction.