THE system is the collection of use cases.
A clock is often used as an actor that triggers the passage of time, or
some time event.
If you are modeling printing as something the system does then you have
entered the "dark side" of use case modeling. Printing is another form of
rendering something to the user, much like displaying. Steps in a use
case description may refere to rendering, displaying or printing some
entity, but I would caution about making it a separate use case from the
start.
Use case models focus on the actors (users), user goals in relation to
interacting with the system under study and what the system offeres up as
value to them. Do not focus on internal system structures.
You can jump over to the dark side and state that any System has only
three use cases: receive inputs, process inputs, transmit outputs, but
this model does NOT acheive any of the values and goals of use case
modeling.
What we are looking for is application-level content so as to make more
informed architectural decisions.
On Mon, 26 Feb 2001, Eric D. Tarkington wrote:
>
> 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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