Use Cases

When a user communicate with the system and system responds it , a use case is formed.Usecase is generally a list of actions/events representing the communication between a system and an actor/actors to achieve a certain goal.

Use cases can be understand very clearly when one knows about the whole process of communication between system and an actor.So one should be familiar with the following process terms:

• Usecase ID: A unique ID for use case
• Usecase Name: Name of the use case 
• Actor : Person/System interacting with system  
• Brief Description:Overview of the usecase
• Precondition:The condition what prompts an actor to start the usecase
• Basic/Normal flow:Flow of the usecase from thescratch
• Alternative flow
• Exception
• Post condition

Use case can also be understand in the visual/diagram form with the help various visualization tools or UML tools like Visio,draw.io etc., the diagram so formed is called Use-case Diagram

For example :User interaction with ATM.

The main purpose of a use case diagram is to show who interacts with your system, and the main goals they achieve with it. Create Actors to represent classes of people, organizations, other systems, software or devices that interact with your system /subsystem.

UML Use Case Diagrams. Use case diagrams are usually referred to as behavior diagrams used to describe a set of actions (use cases) that some system or systems (subject) should or can perform in collaboration with one or more external users of the system (actors).

A primary purpose of the model of business use cases and actors is to describe how the business is used by its customers and partners. Activities that directly concern the customer, or partner, as well as supporting or managerial tasks that indirectly concern the external party can be presented.