Common Mechanisms of UML

Use Cases 

• When we build systems/applications that are usage-centric (Example: Database-oriented, UI-centric applications), the first step is to analyze its requirements by organizing them around the different ways the features are used by the users 
• Once the analysis results are documented, they will be used as inputs to design and implement the solution 
• The different ways in which a mobile phone is used by users 

Make calls 

Receive calls 

Send message/image 

Receive message/image 

Store details of contacts (store, edit, retrieve, delete) 

Capture a picture 

Send an e-mail 

Receive an e-mail

What is each item in the list? 

Each is: 

• A way of using a system to do something useful or valuable to the user 
• A way for a user to interact with the system to achieve a goal 
• A valuable end-to-end service provided by a system to a user 
• Each is called a 'use case’
• Graphically, a use case is represented as an ellipse

What Use case are NOT? 

• Use cases are not functional decomposition 

Example: Finding the districts of a state, finding the role of a user, finding age based on date of birth.

• Steps of an end-to-end service is not a use case 

Example: Adding an item to a shopping cart is not a use case; instead, 'Place order' is. 

• Each alternative is not a use case 

Example: Remove an item from shopping cart, changing the quantity or shipping/payment info, etc.