Re: Use Cases

On 30 Mar, 22:32, "H. S. Lahman" <h.lah...@xxxxxxxxxxx> wrote:
Responding to Bui...

Everything I've read tells me that "Log On" isn't a good use case
either because it doesn't yield value or because nobody would only
want to "Log On". This seems reasonable.

I've worked with systems where pushing the ON button had 100 KLOC of
code behind it. It all depends on what functionality is associated with
"Log On". If "Log On" involves a dozen distinct, logically related
activities then those activities deserve to have their own use case.

The point of use cases is to organize requirements in a manner that
facilitates correct implementation of the requirements. So, in the end,
whatever does that is the right thing to do.

FWIW, I would expect "Log On" to be a use case almost always. It is hard
to think of such a process that would not involve a special UI element
(e.g., a GUI login dialog for user ID and password), saving some state
information (i.e., the user's identifier), AND causing a particular
display to be presented in the UI once the login is completed. In
addition, if there is a need for a login procedure at all, there will
very likely also be a need for some sort of user verification (e.g.,
password authentication) and privilege allocation or infrastructure
initialization. However, ...

So the "Log On" bit has to appear inside other use cases. Does this
mean its description has to be repeated over and over? If it is a
"chunk of function" that can be reused, what is this called? It can't
be a use case because that has to yield value.

The "Log On" use case probably isn't a primary standalone use case. I
would expect it to be included in other use cases that perform more
general activities. IOW, executing the "Log On" activities is an
annoying prerequisite for what the user really wants to do with the
software.

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H. S. Lahman
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I agree with everything you said. So why do the books I've read
(Fowler, Spence & Bittner, Muller, Alhir, Eriksson & Penker) all trash
the idea?

.

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