use case is a bridge between you and customers . so it is divided by yours.
and it is only a way of communication between yours . so .....you should realize
customers idea clearly and map into your use case diagram.
use case diagram could be transferred into collaboration diagram related some classes firstly .and according to this ,you could do step by step.
li run dong <uml oo anylse and design>
it is maybe explained clearly . but it is not complete.
firstly .actually you lack some knowledge . (software engineering , design pattern , uml specification, software architecture , component basic technology. )secondly , rose is just a tool .it depends your experience somehow.
thirdly , all kinds of diagram are based on theory and unbiased cogintion .
they are integrated by three cowmen .they are one .this point is very important .