I disagree that using the <<include>> is effectively functional
decomposition. When you create your use cases, you usually write the basic
path and alternate paths for that use case in as much detail as is deemed
necessary. When you have several use cases, you may find looking at these
paths, that there are a number of "chunks" that are identical in them.
These sections can be pulled out into separate use cases, and the
<<include>> relation used to indicate that the original use cases will
include the included use case's path(s) at some point during its path
(whether basic or otherwise).
We made the mistake of detailing every menu option, etc. that the
administrator could do for our system as use cases and ended up with around
130. Following many discussions this was deemed functional decomposition
(e.g. "Open File", etc.) and the rework resulted in just 16 use cases which
described exactly what the primary users of the system actually wanted to
do, with lengthy descriptions in each. The functional decomposition came
during the design phase when functionality became obvious but was
unnecessary at the analysis phase, i.e. the use cases.
I do agree that having a use case called "Manage System" is appalling. If
the include'd use cases are examined carefully, then hopefully only a few
use cases will come about as a result which is the primary functionality
that the primary users are going to do with the system.
There is a document on http://www.rational.net discussing use cases and
functional decomposition which is well worth a read and certainly turned
our project around for the better - and we did originally have the dreaded
"Manage ..." use cases but no more!!!
Hope this helps.
H
Anna Zee
<[EMAIL PROTECTED]> To: "'Jan Frederik Solem'"
Sent by: <[EMAIL PROTECTED]>,
owner-rose_forum@ra "'[EMAIL PROTECTED]'"
tional.com <[EMAIL PROTECTED]>
cc:
Subject: RE: (ROSE) High level use
case
11/10/2001 14:07 model
Please respond to
Anna Zee
++++++++++++++++++++++++++++++++++++++++++++++++++
Please read the disclaimer at the bottom of this e-mail.
++++++++++++++++++++++++++++++++++++++++++++++++++
I agree with Jan. There should be a package of use cases called Manage
System.
It is possible to break down use cases by using <<include>>d use cases.
Sometimes this is useful but it _is_ effectively functional decomposition
and should never be over-indulged. If the end result is intended to be
an OO designed system functional decomposition should be used sparingly.
It would, IMHO, _not_ be appropriate in this case to have a use case
called Manage System which then <<include>>d all use cases for managing
the system.
-----Original Message-----
From: Jan Frederik Solem [mailto:[EMAIL PROTECTED]]
Sent: 10 October 2001 19:05
To: ROSE_FORUM
Subject: RE: (ROSE) High level use case model
> 1. If I am trying to model a large number of use cases can I create a
> high level use case diagram with say 4 use cases and then expand each of
> those use cases in a separate use case diagram. For example:
> Can I have a use case in my high level use case diagram called 'Manage
> system', and then have a separate use case diagram for 'Manage system'
> showing 8 or 10 use cases?
Well, yes and no. Functional decomposition is exactly what you want to
_avoid_ when modeling with use cases; you can't create "high level use
cases".
But on the other hand you are allowed to group use cases, actors and
use case diagrams into several _packages_ - and thus accomplish what
you seem to want.
> 2. If this is the correct way to model a large system how do I do this
> in Rose? I have tried creating the above scenario but Rose will not let
> me put the 'Manage system' use case in a sub-folder by dragging and
> dropping it onto the navigation screen on the left.
Well, it isn't the correct way - so...:-)
> 3. If this is wrong how do I draw a use case diagram say with 40 or 50
> use cases?
You can have a large number of actors and use cases in your model without
necessary having to put them all in one big diagram, although some SoDA
templates. A use case diagram is not the same thing as a use case model,
and you don't necessarily need a use case diagram giving a global view of
all use cases and actors in the system.
A use case model is the collection of all your use cases, actors,
associations
between use cases and actors, and all use case diagrams created, to model
the functionality of your system.
Best regards,
Jan Frederik Solem <[EMAIL PROTECTED]>
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