State Transition Diagrams

1
State Transition Diagrams

• Depicts object behavior across use cases
• State collection of values of attributes
• State-behavior relationship
• state is updated by some behavior carried out
• Notation
• States rounded rectangles
• Arrows state transitions
• Labels on Arrows event/action/use case

2
Example 1Book in a Library System
start
Reserved
Borrowed
New
Librarian activates book as available
Borrower returns book
Available
3
Example 2 Claim in an Insurance System
start
Rejected
Closed
Pending
Customer Disputes Evaluation
Officer Confirms that Premium Payments OK
Approved
4
When to DrawState Diagrams

• State diagrams are good at describing the
  behavior of an object across several use cases
• Use state diagrams only for those classes that
  exhibit interesting behavior, often the main
  classes of the system

5
State Diagrams Help Complete System Design

• State diagrams often reveal use cases overlooked
  in earlier analyses of the system
• State diagrams provide hints on which attributes
  are necessary for a given class

6
Back to Group Exercise

• Draw a State Diagram for the Table class (and
  others that you find helpful) in the Restaurant
  System
• Take note of the additional specifications
  provided