Use cases alone, however, are not enough. Identify classes that are part of the domain being modeled. Experiment with different approaches. In searching for your project's classes, a single technique is seldom sufficient. Define the responsibilities and relationships for each class in the domain.
Responsibilities are the strategic goals of a class.
Do NOT start with data and try to derive class operations from that. That's called data modeling, not object modeling. Construct the domain class diagram. Together with the responsibility definitions, this diagram lays a foundation for a common vocabulary in the project. Capture all identified use case and class definitions in an OO CASE tool.