Triggers, Events and Signals

[beginner]

From EA's glossary in the help:

event
The specification of a significant occurrence that has a location in time and space. In the context of State diagrams, an event is an occurrence that can trigger a transition.

signal
The specification of an asynchronous stimulus communicated between instances. Signals can have parameters.

Trigger itself is not defined.

b.

[DanG83616]

What? Read the product documentation? How will I ever invent anything?

It would seem more straight forward to make Trigger and attribute of Transition. In that sense the Trigger attribute would be of type Event; it would be an instance of an Event. An Event, being a specification, would have sub classifications of Call, Signal, Change, and Time. Actually Call and Signal might be subclasses of Message. Call would map to a port with a provided interface and Signal would map to a port with a required interface.

I wonder if we could come up with a graphical syntax for representing this stuff. Oh, there I go inventing again.  

This discussion has helped and I think I'm ready to make a profile to codify the above. I still wonder why Sparx did what they did with the Trigger dialog. It implies some alternate rational than the above scheme reflects.

[RoyC]

Dan

Did you read this topic in the Help? (Sorry, I know you want to be a Hoopy, Froody kind of guy, but just assume that the Help, too, begins with the words "Don't Panic".)

http://www.sparxsystems.com/enterprise_architect_user_guide/8.0/modeling_languages/trigger_element.html

You can create Triggers as properties of Transition relationships, and they are of type CallEvent, SignalEvent, ChangeEvent or TimeEvent (although EA code gen for state machines currently only supports the last two).

You shall go to the ball. Sorry about the planet though.

[DanG83616]

Who doesn't strive to be a really hoopy frood?

The main thing that confused me is that a signal is treated as a separate thing from event. I now understand that a Trigger is an instance of an Event. A SignalEvent is a kind of Event whose instances are created by the occurrence of a Signal (as opposed to a call, change, or time) coming from a specific port or ports. The Signal gets its own spec.

Honestly, I don't think the Help would have cleared this up for me but what it says is accurate. Very often, the Help helpfully states things like: "Port -- Use this field to specify a port." Whew! Good thing I didn't try to put a Component in there...

Thanks,
Dan

[DanG83616]

I still didn't get it right in my last post. I left out the key point that KP and Geert both made about Trigger specifying Event/Behavior relation.

Events occur. Events may or may not cause Behavior. A Trigger specifies an Event/Behavior pair, plus optional Constraints.

Revisited this because of new comments in the LinkedIn UML Professionals group where I posed the same question.

Dan