:? There are how many types of use case diagrams? 1 overview use case diagram and many expanded(detailed0 use case diagrams. I have problems in breaking down into how many levels? I need help in this?
See it as grouping. For example you will have a high level diagram that consist of a subject boundary and approx 5 packages.
The packages are the subject bounaries of your next diagram etc etc.
I generally use as rule not more than 5 use cases or packages in a subject boundary.
So how many levels? Well that is up to you, it depends what business process you describe aslong levels do not dictate sequence (solution) you be ok.