I agree 100% that Time (or some variant of it) is the Actor. An Actor is any external
person or thing that will cause some sequence of events to occur within the system.
The Actor is external to the system boundary. The system is the application that you
are building. Just the application, not the underlying o/s, unless you want to define
it that way, which would open a whole bag of worms.
The Time event occurs, the system does its thing and returns control back to Time
where it waits for the next time event to occur. This is also one of those areas where
an Actor document is very helpful in defining just what the role of the Actor is.
John Hebley
Hebley & Associates
-----Original Message-----
From: "Michael Hill" <[EMAIL PROTECTED]>
Sent: Thursday, March 22, 2001 8:59 AM
To: "Shields James" <[EMAIL PROTECTED]>, "Frank I. Reiter" <[EMAIL PROTECTED]>,
<[EMAIL PROTECTED]>
Subject: RE: (ROSE) Use cases: When its not clear who gets the value
Well yes initially, but then no. I don't have a good look at the system
that is being build. I said COULD by used not necessarily be used.
Read my whole explaination not just the first part.
I would have to question, why their is a Trigger and who would get the
result of this trigger. Time trigger is just an implementation. I
guess what I am trying to say is that lets look beyond the
implementation of a Time Trigger, and lets look at the result of this
trigger and who is interested by this. This interested party would be
the actor.
Original Message
From: Frank I. Reiter
Sent: Wed 3/21/2001 3:41 PM
To: [EMAIL PROTECTED]
Cc:
Subject: (ROSE) Use cases: When its not clear who gets the value
Michael
Do you really see Time as an Actor?
I tend to think of Time as a Trigger.
I would be interested in hearing more.
Thanks.
James
Original Message
From: Michael Hill [ mailto:[EMAIL PROTECTED]]
Sent: Thursday, March 22, 2001 1:32 PM
To: Frank I. Reiter; [EMAIL PROTECTED]
Subject: RE: (ROSE) Use cases: When its not clear who gets the
value
Lets remember what the sytem boundaries are to the system that
you are
building. Time is orginated from the OS and below, so an actor
of Time
could be used. I would be careful how I describe the actor of
Time. A
clear definition should be documented for the actor Time. It is
really a
common problem that I have seen. I have seen several systems
deing defined
that an actor Time is needed. But also you should look at it a
bit farther,
it is Time or something else. Does the result get passed back
to an another
actor? If so, that actor will initiate that Use Case.
I hope this sheds some light on this.
Original Message
From: Frank I. Reiter
Sent: Wed 3/21/2001 3:41 PM
To: [EMAIL PROTECTED]
Cc:
Subject: (ROSE) Use cases: When its not clear who gets the value
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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