Richard -
Re: Just like a Java class may implement different
interfaces, an actor may implement (or play) different roles.
While this is a true statement, I believe that the roles should be modeled
as separate actors until and only if combining them adds to comprehension of
the intended system usage and behavior. Premature combination can yield
unforseen side-effects. When such combination is done, it probably should
be done by way of extension relationships (e.g., if the roles of actors A
and B are to be combined, I suggest defining actor C as extending both A and
B; this articulates the decision explicitly and allows for retraction of the
decision at a later time).
Re: Do you have any favorite techniques to support this distinction when
modeling?
Not that one could codify into a cookbook; experience plays a big part in
this. One strong advisory would be to be diligent in resisting the urge to
define relationships between actors, per se, until the roles have been
defined quite clearly; this helps to prevent actors from accumulating
inappropriate rights and responsibilities. Once the actors' roles are well
understood AND DOCUMENTED, inheritance and other relationships among them
may be appropriate to model. Bear in mind that the relationships between
actors are *outside* the system, and should be represented only to the
degree that doing so aids in definition of the system's usage and behavior.
Re: Have you got the tools to work with you on this?
The modeling constructs used are sufficiently fundamental that I've had no
significant problems getting Rose to provide adequate support.
Re: When you model in
Rose, do you name your actors by their role, do you name the actor's role
based on associations to use cases, do you use stereotypes? Do you inherit
roles or actors, or do you have separate hierarchies?
I've been all over the map on these, as my experience has grown, and as
different circumstances have presented themselves. No particular rules of
thumb come to mind. The circumstances and complexity of the problem tend to
dictate the approach. One general heuristic that may help is to focus work
(and detail) in the areas that are least well understood, because this is
where the most valuable results will be obtained.
Re: If you use IUCM
(ReqPro-Rose)have you had any difficulty capturing the distinction between
actors and the roles they play?
I don't generally use RequisitePro, because I haven't perceived it to add
much value to the articulation of the problem. Most functional requirements
are best described by the text of use cases, and the remainder tend to be
the "ilities", which tend to be small in number and can be asserted
adequately in text notes and/or documentation fields.
One final observation: The requirements discovery and articulation activity
is at once both the most important and least respected portion of the work
to be done in developing a system; it must be allocated plenty of time and
resources (including potential users, or, failing that, persons who can
function as proxies for real users with a high degree of fidelity), if the
resulting system is to be a success.
- Al
-----Original Message-----
From: Richard Howlett [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, July 17, 2001 9:42 AM
To: [EMAIL PROTECTED]; [EMAIL PROTECTED]; [EMAIL PROTECTED]
Subject: RE: (ROSE) Access levels
Hi Alan,
That's good advice. Actors are implementation-related concepts, roles are
specification-related. Just like a Java class may implement different
interfaces, an actor may implement (or play) different roles.
Do you have any favorite techniques to support this distinction when
modeling? Have you got the tools to work with you on this? When you model in
Rose, do you name your actors by their role, do you name the actor's role
based on associations to use cases, do you use stereotypes? Do you inherit
roles or actors, or do you have separate hierarchies? If you use IUCM
(ReqPro-Rose)have you had any difficulty capturing the distinction between
actors and the roles they play?
curious,
-Richard
>From: "Cote, Alan T" <[EMAIL PROTECTED]>
>Reply-To: "Cote, Alan T" <[EMAIL PROTECTED]>
>To: "'payam` zahadat'" <[EMAIL PROTECTED]>, [EMAIL PROTECTED]
>Subject: RE: (ROSE) Access levels
>Date: Tue, 17 Jul 2001 08:09:22 -0400
>
>
>To help prevent confusion while analyzing the requirements (modeling the
>use
>cases), especially, I recommend defining the actors based upon their
>*roles*
>when interacting with the system. If the distinctions among roles are made
>with sufficient attention to detail, you may find that there are
>significant
>differences between them in the system design. Conversely, you may find
>that some of the distinctions between roles are insignificant, leading to a
>decision to combine them. This is a very important aspect of system
>analysis. How the different roles are to be distinguished/represented in
>the design and implementation should be decided only after the interactions
>and roles are well understood.
>
>-----Original Message-----
>From: payam` zahadat [mailto:[EMAIL PROTECTED]]
>Sent: Tuesday, July 17, 2001 4:24 AM
>To: [EMAIL PROTECTED]
>Subject: (ROSE) Access levels
>
>
>
>Hi
>I have some users with different privilages to access
>to the system like administrator,users with special
>tasks,... .
>their privilages may be change some time in the future
>or not, Which is better: one actor for all users of
>the system(include admin,...),or seperate actors for
>each ?
>if the new groups of users migth be specify ,which one
>is better?
>Thanks
>
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