Common Mechanisms of UML

Use Case Model 

Actor

• Actor is something external to the system and interacts with the system 
• Actor may be a human being, device or some other software system 
• For library system, actors might be a 

➤Librarian 

➤Borrower 

Use case 

A use case represents sequence of actions performed by the system that yields an observable result of value for a particular actor. Use case represents a functional requirement of a system.

For library system, we can find the following use cases 

• Login 
• Search 
• Browse 
• Checkout item 
• Return item 
• Make reservation 
• Cancel reservation 
• Manage titles 
• Manage items 
• Manage borrowers 
• Manage librarians

Use Case Diagram

• Use case specification. Login
• Use case specification. Browse
• Use case specification. Search
• Use case specification. Make reservation 
• Use case specification. Remove reservation 
• Use case specification. Checkout item
• Use case specification. Return item