Les,
There isn't much snow, but we're just coming out of a blistering cold
snap. Extreme cold is the secret source of the well-known Canadian
goodness. (Don't taunt me with reports of balmy weather, please.)
When we install 2001 at the college, I'll probably hunt up a "Father
Time" icon, and you will be one of the first to know.
Your point seems to be that you can define the system boundary as seems
best, even excluding elements of what is commonly called "the system".
I'm inferring that GUI's and OS's (or selected parts of their services)
can be deemed outside the system boundary without going over to the dark
side. In all the circumstances, using the word "system" to name an
actor may be within your design authority, but it probably creates
controversy for no good purpose.
Not bad. I think I can sell it to my young iconoclasts.
-Eric
[EMAIL PROTECTED] wrote:
>
> Eric,
>
> How's the snow?
>
> If you to treat anything (legacy system included) as an actor, simply take
> it outside the system boundary. You're only interested in developing what's
> inside the system boundary.
>
> I like the 'Father Time' icon. Let me know if you find one.
>
> Les.
>
>
> To: <[EMAIL PROTECTED]>
> cc: [EMAIL PROTECTED]
> Subject: Re: (ROSE) "System" as Actor
> Sent by: [EMAIL PROTECTED]
> 02/26/2001 04:15 PM
>
> Les,
>
> Maybe I should have made this a bar bet, but I do those when I have a
> (secret) opinion firmly formed on the controversy.
>
> Does the system include the system boundary? If so, is the system
> within the system? If the system is not within the system, can it be
> said to be external to the system? If the system is external to the
> system, and communicating with itself, why can't it be an actor?
>
> Probably, most people would say that the system *is* within the system
> boundary, so it can't be an actor.
>
> Is it true that I can't treat anything within the system as an actor?
> If I can treat an "untouchable" legacy subsystem as an actor, why not
> the system?
>
> Using "Time" instead of "System Clock" as an actor is an interesting
> idea -- sort of an Ingmar Bergman thing. The "grim reaper" has already
> been used for death, but "father time" is very similar -- do you think
> it would be suitable as an icon?
>
> In the end, best practices can include some arbitrary standards, and I
> can accept that.
>
> -Eric
>
> [EMAIL PROTECTED] wrote:
> >
> > Eric,
> >
> > I think the problem could be caused by 'your students' not having a firm
> > idea as the scope of the system.
> >
> > You might try drawing a context diagram where everyone contributes and
> > agrees to the exact boundary to your system.
> >
> > As for system clock, as an actor, the actor is 'Time' and produces an
> input
> > to your system clock.
> >
> > The printing issue comes about as a result of not having system scope
> > defined. I.e. Is the Printer inside or outside your system? You decide.
> If
> > it's outside, the printer can be an actor, if it's inside then the actor
> > is/maybe the printed output or the person the output is for, depends very
> > much on why you're sending it to the printer.
> >
> > Hope this helps,
> >
> > Les.
> >
> > 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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