Lecture Notes: UML State Machine Diagrams

Introduction to UML State Machine Diagrams

• UML State Machine Diagrams are used to represent the state transitions of entities in software.
• Entities move from one state to another, capturing their lifecycle.
• Example: A bank account can be suspended, active, closed, or under scrutiny.

Lifecycle Examples

• Human Lifecycle: Birth, infancy, childhood, adolescence, youth, middle age, old age, infirmity, death.
• Software systems often have non-linear state transitions.

Notation and Terms

• Initial State: Where the state machine begins; multiple initial states are allowed.
• Final State: Only one final pseudo state is allowed.
• Comment or Note: Annotations in the diagram.
• Decision: A gateway that leads to multiple paths.
• State: Represents a condition or situation during the life of an object.
• Composite State: Contains two or more substates.

Preparing a State Machine Diagram

1. Identify business entities to be modeled.
2. Identify various states of these entities.
3. Identify transitions between states.
4. Identify permanent states.

Case Study: Insurance System

• Policy Lifecycle:
  • Proposal submitted ➔ Underwriting team.
  • Policy issued and serviced by paying premiums.
  • Policy lapses if premiums are unpaid.
  • Lapsed or paid-up policies can be revived.
  • Upon death or contract completion, policy terminates, benefits are paid.
• Additional Features:
  • Endowment plans can be pledged for loans.
  • Policy may be assigned to insurance companies and reassigned upon loan repayment.

Creating the State Machine Model

• Start with initial state.
• Use tools to choose UML state machine model.
• Change design orientation if necessary.
• Diagram states such as "being underwritten," "in force," "lapsed," "paid-up," and "terminated."
• Identify transitions like policy revival.

Key States and Transitions

• From "being underwritten" ➔ "in force."
• From "in force" ➔ "lapsed."
• Lapsed policies can become "paid-up" or "revived."
• Policies can terminate from "lapsed," "paid-up," or "in force" states.

Composite States and Internal Behavior

• Composite states have internal substates.
  • Example: "Applicant" state with substates "pending legal check" and "payment processing."
• States can specify entry and exit points and conditions.

Conclusion

• State machine diagrams are created early in the analysis phase.
• Composite states and internal behaviors provide detailed control over transitions.

End of lecture notes.