What is the Purpose of Use Case Modeling?
A use case diagram is shows a set of use cases, actors, and their relationships to each other. It describes how users want to use a system which allows us to know:
who the relevant users of the system are,
what services they want the system to provide, and
what services they need to provide to the system.
It is used to describe the functional requirements and usage scenarios of the system to be developed.
It facilitates the progress of work in the various phases of the development process.
It is used to verify and validate system requirements.
Use case modeling is a good way to perform system requirement analysis. Through it, system analysts and users can better communicate system requirements.