UML25 — Location: 18.1.3 Semantics Use Cases and Actors P. 685 - Are actors mandatory?

current text: “A UseCase is the specification of a set of behaviors performed by a subject, which yields an observable result that is of value for one or more Actors”
Other than this and the next paragraph, there is no indication that an actor is mandatory, e.g., no OCL, no relationship on the diagram. Consider updating the Figure 18.1 UseCases to show a relationship between the actors and usecases to make a use case require an actor.

In addition, this is contradicted by p 686, which says: “UseCases may have associated Actors,”, which seems to indicate that actors are not mandatory.

So
• Make the text consistent between 685 and 686
• Consider updated Figure 18-1 to show at least one actor
• Consider adding OCL to force at least one actor.

Changing the multiplicity or adding a constraint would be inappropriate because it could break existing
models, so change the wording.
This also resolves issues 18079 and 18080