Class Diagrams (p. 114)

Static structure of an object-oriented program containing

• attributes
• constructors
• methods
• relationships among classes and objects

May be

• created as a design or analysis doc before coding
• generated from existing source code

Relationships Between Classes

Two groups:

1. class-level relationships
   • inheritance
   • implementation
2. instance-level relationships
   • dependencies
   • association
   • aggregation
   • composition

Class-Level Relationship

Inheritance is also called generalization because the subclass/type is a specialized form of the superclass/type. The implementation relationship between a class and an interface means the class implements the interface.

Instance-Level Relationship

• Dependency
  • points from the client element to the server element
  • changes to the server may cause changes to the client
• Association
  • family of links
    • bi-directional (line)
    • uni-directional (directed line)
    • aggregation (includes composition aggregation)
    • reflexive (on the same class)
  • Can include:
    • role names
    • ownership indicators
    • multiplicity
    • visibility
    • etc.
• Aggregation
  • specific binary association representing a part-whole or part-of relationship
  • contained class does not have a strong lifecycle dependency on container
    • a teacher has students
    • destroying a teacher doesn't mean destroying students
• Composition
  • aka composition aggregation
  • stronger form of aggregation
  • considered as a "physical containment" relationship
  • when container is destroyed, contents are destroyed

Multiplicity Notations