A Practical Guide to SysML, 2nd Edition

12.4 Using Use Cases to Describe System Functionality

A use case describes the goals of a system from the perspective of the users of the system. The goals are described in terms of functionality that the system must support. Typically, the use case description identifies the goal(s) of the use case, a main pattern of use, and a number of variant uses. The system that provides functionality in support of use cases is called the system under consideration and often represents a system that is being developed. The system under consideration is sometimes referred to as the subject and is represented by a block. We will use the term system or subject interchangeably to denote the system under consideration.

A use case typically covers many scenarios ...