Use Case Modelling

Use Case Modelling is a very popular technique to find out user requirement
Use cases describe the system from the user's point of view
A use case defines the interactions between external actors and the system under consideration to accomplish a goal
It describe the interaction between one or more actors and the system itself represented as a sequence of simple steps
There are main formats used to express use cases: High-Level format and Expand format

A High-Level use case describes a process very briefly. This format is typically useful during the early stages of a development project.
An Expanded use case describes a process in more detail than a high level description. An expanded use case description includes a step by step description includes a step by step description of the typical course of events for the use case. It is sometimes useful during requirements gathering and analysis.

A use case defines a sequence of actions performed by a system that yields and observable result of value to an actor
A use case is always initiated by an actor
A use case provides value to an actor
A use case is complete

The Actor

An actor is usually drawn as a named stick figure, or alternatively as a class rectangle with the keyword