Hi:
I teach the Rational OOAD class and we discuss in great detail just
questions like this. In a nutshell:
1) External system as an Actor, good. I agree.
2) Use Case called calculate tax, good. I agree.
3) The actor only sees the "interface", externally visisble actions. OK
4) here we diverge just a small bit.
Use Cases are intended only to tell you what to do from the actors
point of veiw. In the use case explain what the Actor gets and gives.
In the use case specification give the main flow and any alternate flows
and any exceptions. Only say what to do NOT HOW TO. You may want to add
a activity diagram to show main flow and alternate flows. Use very little
detail at this point.
THEN
Create one or more "use case realizations" You may have two or more
instances
of the actors that can perform the tax calculations. ( one for USA, one for
each state,
one for British ... and so on )
Each use case realization will have the details of the messaging. The use
case
realization would have the detailed sequence diagrams and detailed activity
diagrams
of HOW the actor is called. I would probably make a subsystem the
encapsulates
all of the detail.
Each operations would get a precondition and a postcondition. Also the
semantics would
be modeled. This is where I would put the details of each message, that is
the format.
Each parameter and return type would be explained. What causes an exception
and what
what the exception does.
There is more,
but that is all that you get for free ;-)
Eric Aker
-----Original Message-----
From: Williamson, Rusty [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, March 21, 2001 10:22 AM
To: 'Rose Forum'
Subject: (ROSE) UML question number two
Hello,
We have a situation where we must query tax information from an external
system. We know that this query must be made up certain messages and that
the messages will have certain formats. How does this all pertain to the use
case model? We have made the external system an actor, and we've created a
use case called calculate tax. The specification says that use cases shall
contain only externally visible actions from the actor's point of view. Do
we model and specify these messages within the use case model? And how
about the message formats? Where do we specify these?
Thank you for any help that you can give me!
Rusty
---------------------------------------------------------------
Rusty Williamson
Sr. Systems Architect
Corporate Office
GERS, Inc.
10431 Wateridge Circle * San Diego, CA 92121
(800) 854-2263 * CA (858) 457-3888
FAX (858) 484-9237 * Desk (858) 484-9237
E-mail: [EMAIL PROTECTED] * Web http://www.gers.com
"e-Business Solutions for the Consumer-Driven World"
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