UML Diagrams in Software Design

UML Diagrams

Class Diagrams

• Used to describe the structure of a system
• Displays classes and their relationships
• Classes are represented as rectangles with three compartments:
  • Top: Class name
  • Middle: Attributes (data)
  • Bottom: Operations (methods)
• Relationships between classes:
  • Inheritance (generalization): arrow with open arrowhead
  • Composition (containment): filled diamond
  • Association: line with arrowhead

Use Case Diagrams

• Used to describe the functional requirements of a system
• Displays actors, use cases, and their relationships
• Actors are represented as stick figures
• Use cases are represented as ovals
• Relationships between actors and use cases:
  • Communication: line between actor and use case
• System boundary: rectangle surrounding use cases

Sequence Diagrams

• Used to describe the sequence of events in a system
• Displays objects, lifelines, and messages
• Lifelines are represented as vertical dashed lines
• Objects are represented as rectangles at the top of the lifeline
• Messages are represented as arrows between lifelines
• Time increases from top to bottom

Activity Diagrams

• Used to describe the flow of control in a system
• Displays actions, decisions, and control flow
• Actions are represented as rectangles
• Decisions are represented as diamonds
• Control flow is represented as arrows between actions and decisions
• Swimlanes: vertical or horizontal partitions dividing the diagram

State Machine Diagrams

• Used to describe the behavior of an object over time
• Displays states, transitions, and events
• States are represented as rectangles
• Transitions are represented as arrows between states
• Events are represented as labels on transitions
• Initial state: black circle
• Final state: circle with a concentric circle

UML Diagrams

• Types of UML diagrams: Class, Use Case, Sequence, Activity, and State Machine diagrams

Class Diagrams

• Describe the structure of a system
• Display classes and their relationships
• Class representation:
  • Rectangle with three compartments
  • Top: Class name
  • Middle: Attributes (data)
  • Bottom: Operations (methods)
• Relationships between classes:
  • Inheritance (generalization): arrow with open arrowhead
  • Composition (containment): filled diamond
  • Association: line with arrowhead

Use Case Diagrams

• Describe the functional requirements of a system
• Display actors, use cases, and their relationships
• Actor representation: stick figures
• Use case representation: ovals
• Relationships between actors and use cases:
  • Communication: line between actor and use case
• System boundary: rectangle surrounding use cases

Sequence Diagrams

• Describe the sequence of events in a system
• Display objects, lifelines, and messages
• Lifeline representation: vertical dashed lines
• Object representation: rectangles at the top of the lifeline
• Message representation: arrows between lifelines
• Time increases from top to bottom

Activity Diagrams

• Describe the flow of control in a system
• Display actions, decisions, and control flow
• Action representation: rectangles
• Decision representation: diamonds
• Control flow representation: arrows between actions and decisions
• Swimlanes: vertical or horizontal partitions dividing the diagram

State Machine Diagrams

• Describe the behavior of an object over time
• Display states, transitions, and events
• State representation: rectangles
• Transition representation: arrows between states
• Event representation: labels on transitions
• Initial state: black circle
• Final state: circle with a concentric circle