Frank
This is a very common problem, and for me, one that UML does not adequately
address.
I would agree with you that Time is not an Actor.
Rather, it is a Trigger.
I also agree with you that your System is not the Actor.
That would completely miss the point about Actors.
There is an excellent little book by Martin Fowler called UML Distilled
(ISBN 0-201-32563-2) that discusses this problem.
And, he proposes a number of solutions.
In these cases, I tend to consider the User Role/Department/Other System
that benefits most DIRECTLY from the Use Case.
When your System does its check, who is it done for?
HTH
James Shields
>>>>>>>>>>>>>>>>>>>>>>>>>>
I'd like to hear some opinions about how to handle something that has me a
bit stumped.
I am writing use cases for a system. For the most part I am finding that
pretty straight forward. In one instance however there is behaviour that I
want to document and I can't see quite how to make it a use case. (On
possible answer is that I shouldn't try!)
The system has a cache of data which originates elsewhere and can change
over time. Periodically the system checks with the source of truth for
updates. The question that really stumps me is "Who is the actor in this
use case?"
The obvious answer is time or the system clock. I don't really want to do
that because the rule of thumb that resonates best with me is that the actor
is a party outside of the system that gets value from the use case. Time
gets no value from this.
So who does?
Well, I could say that the system does. That would make this a use case of
the external system, with my system as the actor, rather than a use case of
my system. That wouldn't really belong in my document.
Various users benefit in that they are working with more up to date data,
but they get that value through other use cases already written. They do
not participate in this use case at all.
How do people handle this?
Frank.
-----
The very act of seeking sets something in motion to meet us;
something in the universe, or in the unconscious responds as if
to an invitation. - Jean Shinoda Bolen
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