1. Use Case Diagram Example
The diagram above has three actors: Patron, Librarian, and Time. It is common practice to use a Time actor to initiate scheduled tasks.
Library Lending System is the target system. It contains tasks named Borrow Item, Check for Fines, Return Item, Mark Items as Returned, Reserve Item and Generate Fine Notification.
An individual in the role of Patron will be able to perform the tasks of Borrow Item, Return Item, and Reserve Item.
An individual in the role of Librarian will be able to perform the activity of Mark Items as Returned and is involved in Borrow Item.
The scheduled events fulfill the role of Time and will be able to perform the activity of Generate Fine Notification.
Use Case Diagrams

2. Activity Diagram Example
Example Activity Diagram
The simple activity diagram above illustrates the checkout process from a public library. The small circle is a start state to indicate where the process begins; the larger one is a end state that indicates where it ends.
The Patron starts with Choose Item(s). Patron does two actions in parallel: present item(s) to librarian and present library card to librarian. The Librarian performs Verify Identity of Patron. The Patron must then present photo id. The Librarian then scan item(s), stamp due date card(s), insert due date card(s) in item(s), present item(s) to patron. The Patron then does verify due date and the process ends.
Use Case Diagrams

3. Class Diagram Example Example Class Diagram
The class diagram above shows an airline flight from the perspective of the airline employees. There are eight classes, five associations, and two generalizations.
The links from Crew to FlightAttendant and from Schedule to Flight are aggregations. The links from FirstOfficer and Captain to Pilot are generalizations.
The class diagram shows the following information:
A Schedule contains a (possibly empty) collection of Flights.
A Flight has exactly one Aircraft and exactly one Crew.
An Aircraft can be associated with any number of Flights. The navigability of the relationship is one directional as indicated by the arrow; Flights have Aircrafts, not the other way around.
A Crew has two or three Pilots and at least one FlightAttendant. The Flight “knows” its Crew but the Crew doesn’t know which Flight instances it is associated with. (That could be a problem)
Pilot is an abstract class and implements an interface (indicated by the italicized name). Both FirstOfficer and Captain inherit from Pilot.
Use Case Diagrams

4. Sequence Diagram Example
In the diagram above, an actor called time sends the calcFines message to scheduler. The scheduler then iterates through its collection of patron objects. A list of loans is retrieved for each patron. We then loop through the list loan objects and ask each loan to calcFine. The loan object delegates that to each of its item objects. And finally each item object uses the calculator object to calculate the fine for the given number of days.
Use Case Diagrams

5. Collaboration Diagram Example
Example Collaboration Diagram
The collaboration diagram above is the semantic equivalent to the sequence diagram example.
Use Case Diagrams

6. State Diagram Example
Example State Diagram
Use Case Diagrams

7. Component Summary
Use Case Diagrams

8. Deployment Diagram Example
It is becoming the norm to distribute complex systems, especially with the popularity of web applications. Deployment diagrams describe how functionality will be deployed in systems by mapping components to the physical environment in which they operate.
Deployment diagrams may describe general or specific deployment characteristics of a system. For example, a deployment diagram may indicate which functionality appears in a browser verses the functionality that appears in the server. The diagrams may describe the details of actual clients and servers as well.
Deployment diagrams are often used by distributors, installers, and maintainers of software to understand the physical environment in which the system will reside. They can be used to indicate change in the deployment environment as well.
Use Case Diagrams