Quick link UC->Actor

[thomaskilian]

Stefan,
as always, this depends. It's probably a bad translation when I use the word trigger. Likely "uses" would be a more appropriate word. That is: "enroll in course" will have student that "uses" the use case (sounds silly) and the schedule is being used. Of course it's almost every time a bidirectional thing but I like to show something which is only possible using the direction. And here EA does not do what I expect.

However, do you know of any "official" rule on how to connect UC and Actor?

[StefanPears]

The use case diagram itself is static. It just shows who (actor) has something to do with the desired behavior, that is described inside the use case. And it shows that the behavior uses additional behavior from other use cases (include, extend). The use case diagram is not a flow.

IMO to "trigger" a use case is OK. This association with the arrowhead pointing from an actor to a use case highlights the one and only one association, that starts the behavior that is expressed in the diagram. Any further flow is inside the use cases.

The OMG's UML2.0-Specification says nothing about directed associations from actor to use case or vv. I guess it was in RUP, where I read it or in a publication about RUP. I'll add it in this forum when I've found s.th. Until then I say, you can go ahead with using directed associations from actor to use case. But only one actor "is involved in AND triggers", all other actors are just "involved in" the diagrams purpose.
Stefan

[thomaskilian]

Thanks Stefan,
I also remember lots of diagrams and (my stomach feeling) is that 75% use an undirected relation. The rest is being used in the trigger notation from Actor to UC. I'm absolutely not sure whether I've seen the UC->Actor relation somewhere else. (I'll keep it anyway

[«Midnight»]

Take a look at Ambler's The Elements of UML 2.0 Style. He has a pretty good take on when and why to use directed associations.