Applying UML Patterns - Confusion

[Muhammad Asif]

Hi all,
i am studing applying uml and patterns (2nd edition).
The last paragrahp of page-45 says
"The UP defines the use-case model within the requirements discipline.
Essentially, this is the set of all use cases; it is a model of system's functionality and environment"
Now what i donot understand is that how-come a use-case model is a
a model of system's environment ???
Thanx
Asif

[Ilja Preuss]

The use case model includes Actors: humans and systems the system will need to interact with. They (at least partly) define the environment the system will work in.

[Muhammad Asif]

Thanx a lot for ur reply.
Any other replies to will be appreciated...
Asif

[Stan James]

An interesting non-UML diagram is a "context diagram" which is just a box that shows which components are inside the system and more importantly which are outside it. The use case model is a form of that, because all actors are outside, and some of them are other systems. If you "zoom out" on the uc model until you just have a box for the system with actors hanging around outside you pretty much have a context diagram.
The context diagram for my current system shows 15 categories (classes, if you will) of systems and protocols we interact with, and some of those categories have dozens of instances. Maintaining this picture keeps me employed.

[Muhammad Asif]

Thanx ....
I have gone thru some other material as well.
Thanx a lot for ur time.
Take Care
Asif

[Ilja Preuss]

Originally posted by Stan James:
An interesting non-UML diagram is a "context diagram" which is just a box that shows which components are inside the system and more importantly which are outside it. The use case model is a form of that, because all actors are outside, and some of them are other systems. If you "zoom out" on the uc model until you just have a box for the system with actors hanging around outside you pretty much have a context diagram.

As far as I know this flavor of Use Case diagram is also called System Boundaries diagram.

[Stan James]

I didn't recall that name, but a quick google on boundary (single, not plural) got me this from Uncle Bob:

Use Cases Diagrams
Of all the diagrams in UML, use case diagrams are the most confusing, and the least useful. With the exception of the System Boundary Diagram, which I’ll describe in a minute,I recommend that you avoid them entirely.
System Boundary Diagram
Figure 5-1 shows a System Boundary Diagram. The large rectangle is the system boundary. Everything inside the rectangle is part of the system under development. Outside the rectangle we see the actors that act upon the system. Actors are entities outside the systemthat provide the stimuli for the system. Typically they are human users. They might alsobe other systems, or even devices such as real-time clocks

www.objectmentor.com/resources/articles/Use_Cases_UFJP.pdf
But I don't see it as one of the Models of the UML. (That sounds so much like a Playboy layout )
[ July 31, 2003: Message edited by: Stan James ]

[Ilja Preuss]

Originally posted by Stan James:
I didn't recall that name, but a quick google on boundary (single, not plural)

Oops... :roll:

www.objectmentor.com/resources/articles/Use_Cases_UFJP.pdf

Yes, that's where I've got it from, too...

But I don't see it as one of the Models of the UML.

Use Case diagrams are the last in the list. He doesn't seem to discuss the different flavors there. He does discuss the boxes in the linked document, though.

(That sounds so much like a Playboy layout )

[ July 31, 2003: Message edited by: Ilja Preuss ]