Subject: Questions about use cases

> 1. Because the use case can not specify the relationship between objects i
> the system we will design, and also it can not deal with concurrency, how
> can we do with these problems?

These problems will be dealt with in the later phases of the software
engineering process.  Why are you so anxious to be dealing with them so early
in the process?  Neither of these notions occurs in the requirements document
for a very good reason: they mean nothing to the intended audience of the Use
Case diagram.

> 2. Because the location the vehicle claims to be can be compared with the
> location of the vehicle observed to be, I know that the location the
> vehicle claims to be is got from the GPS unit in the vehicle, but the
> location of the vehicle observed to be is got from the sensors in other
> vehicle, right?

Right.

> 3. If there is an exception, should we specify the behavior of the
> exception?

If exceptions are specified in the requirements document, then they
should appear in the use cases.