Can you create an extend relationship between actors?

Question

Can you create an extend relationship between actors?

Can you create an extend relationship between a use case and an actor?

I can't find anything online.

Answer 1

The « extend » relationship is exclusively defined between use-cases. It means that in some cases, the use case will be enriched with additional behavior, depending on sole conditions. Technically speaking, the use-case that is extended shall have some predefined extension points where the behavior will be extented by the extension

This relationship makes no sense between actors. However, actors are classifiers and could hence have a specialization relationship, even if this is nit explicitly stated in the UML specs.

This relation also makes no sense between an actor and a use case. Actors are involved in a use case: what would an extension mean? Philosophically speaking you could think (but not write) that every use-case somehow extend actors in the sense that it allows them to do more and allows for interactions (so behaviors that the actor would exhibit) that would not take place without the use-case. But from an UML modelling perspective this would be wrong.