Colin
I have been following this discussion with laziness. Your example increased
my interest in it. We have recently developed an Order management system
which interacts with a couple of other systems (some legacy ones like
SAP/IBM) via messages/data as you mentioned. I tried modeling it using
actors for the systems and use cases for the Order management system which
process those messages although I did not show the polling of messages
(where we used standard software like MQ and STC) and scheduling of use
cases using actors like you suggest. That may be useful. And they do form
part of the system IMHO as they effect its behaviour (by possibly choosing
from alternate use cases...).
Misbah
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Misbah Mirza
www.MetaPack.com
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-----Original Message-----
From: Colin Gourlay [mailto:[EMAIL PROTECTED]]
Sent: 27 February 2001 09:12
To: [EMAIL PROTECTED]
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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