Use cases question.

Hello folks,
I have a question concerning use cases. I have seen that some people write only the user actions, and the system's reply (with the argument that requirements are defined from the view point of the actor), while others write the steps involved to "calculate" the reply, since the system usually requires several steps before generating the reply. (Both are from "professional people")-
What is the standard way of doing it? I just want to have use cases in a school report and I would include the sequence diagram showing how the different objects in the system interact to solve the problem.
Thanks you!

Moving to the Process forum...

Originally posted by Tonny Tssagovic:
What is the standard way of doing it?

There is no standard way, because every project and every team has different needs. What formatlity you need depends on many things: what you are doing them for, on colaboration constraints, risk of the project etc.
For some teams, a couple of words on an index card is all they need. Others feel they need to write pages of formal descriptions.

Sometimes you'll see a use case step reference other documents like a "business rules repository." You might see something like this:
user selects "calculate total"
system calculates total (See BR1234 for calculation rules)
system displays total
This is a neat way to keep your use case at a "consistent level of abstraction" and that's one of my criteria for easy communication in documents, code, IRS forms, etc.

You might find the examples posted at http://www.agilemodeling.com/artifacts/essentialUseCase.htm and http://www.agilemodeling.com/artifacts/systemUseCase.htm to be of help. These pages include both simple and complex versions of use cases. The goal should be to model just enough to be sufficient for your task at hand -- any extra work would be a waste of time.
- Scott

Originally posted by Scott Ambler:
The goal should be to model just enough to be sufficient for your task at hand -- any extra work would be a waste of time.

Well, the problem probably is that the "task at hand" is "pleasing the teacher"...

I don't think anyone answered the original question.
What appears to be the most commonly accepted narrative form for use cases is one that is in the form of "the user does this; then the [application] does this." For example, "the clerk scans an item; the POS station displays the scanned item name and price." Use cases answer the question, "How does the user interact with the system?" By only supplying the user actions, you would only be presenting half of the story.
Be careful not to supply implementation details in the use case document.
-Jeff-
[ March 04, 2004: Message edited by: Jeff Langr ]

Thank you all for your time: Ilja, Stan, Scott and Jeff;I appreciate it.
The problem as Ilja said is there are no real "requirements" but to please the teacher.