Colin,
Have to say, I agree with you. I too am having use cases with part of the
system as an Actor.
In my case I have to write code inside of about six other applications,
have each of these pieces of code communicate whilst the real "actor" makes
some decisions.
The piece of code that ties all the bits together is my non-conventional
"actor". There is no problem, everyone in the organization understands what
is going on.
Purists will always argue about what "should be", realists get things done.
If the tool helps stick to as many conventions as possible, if it make more
sense to use it in another way, do so.
A prime example is Rational's Process Workbench. It was designed to modify
RUP for specific process adaptions. I am using it to completely model my
business side process as it does an excellent job, much better than use
cases as it is more structured and has better ties between artifacts,
actors, process etc. Not what it was designed for and if I slavishly
followed the rules then I would loose an almost perfect tool for my
application.
Mark
"Colin Gourlay" <[EMAIL PROTECTED]>@rational.com on
02/27/2001 04:11:56 AM
Please respond to "Colin Gourlay" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
To: <[EMAIL PROTECTED]>
cc:
Subject: Re: (ROSE) "System" as Actor
This is an interesting question you pose Eric.
I am quite new to UML and have been doing precisely what you're students
have been doing. In a separate post, in recent weeks, where I stated
something to the effect that an actor either gives value to or gets value
from a use case and went on to say that an actor can be external or
internal
to the system under discussion I found that the general consensus of
opinion
was that Actors are external and *not* part of the system under discussion
That is, both your students and myself appear to have been doing this
incorrectly.
I accepted what other posters said *but* I would like to pose pretty much
the same question as yourself but relate it to my own circumstances...
I am writing a middleware application that is to integrate disparate
systems. The system under discussion has to poll other systems and devices
(these were my external actors) and react accordingly upon receiving
messages, data or whatever. In this SuD I had an actor (a stereotyped
class) that was responsible for polling and generally *controlling* the
coordination/sequence of events of the use cases in the SuD. This actor as
I saw it was very much central (not in a behaviourla sense but in a
controlling context) to the system being designed.
As Eric says if it "...looks like an actor, walks like an actor, and quacks
like an actor, what is it?"
Or is this newbie (me) missing something completely??
Regards
Colin
----- Original Message -----
From: Eric D. Tarkington <[EMAIL PROTECTED]>
To: ROSE_FORUM <[EMAIL PROTECTED]>
Sent: Monday, February 26, 2001 9:59 PM
Subject: (ROSE) "System" as Actor
>
> When drawing their first use case diagrams, my students (including some
> of my best) sometimes identify the system under development as an actor.
>
> I've been telling them not to do this, since my favorite sources don't
> do it, but lately it has been bothering me.
>
> When the system is doing something like scheduling activities for
> regular or delayed execution, I have seen authorities use a "system
> clock" actor. Also, in some environments it is quite right to say that
> the system provides services such as printing. If the system looks like
> an actor, walks like an actor, and quacks like an actor, what is it?
>
> -Eric
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