SE450: UML Class Diagrams: Relationships [15/18]

Relationships

• Association
• Generalization
• Dependency
• Constraint Rules

Association - relationships between instances of Types.

• Name
• Role
• Label with direction
• Direction (navigability)- bi-directional or uni-directional
• Cardinality - (multiplicity)

Aggregation

• has-a or part-whole
• open diamond

Composition

• a more limited aggregation relationship
• assumes aggregate class has control over the lifetime of the component
• exclusive ownership of component by aggregate class
• closed (black) diamond

Generalization (Specialization)

• Inheritance (class/class or interface/interface)
• Subclassing
• Realization (class/interface)

• interface-inheritance (subtyping) shown with a dashed line and filled arrowhead
• implementation-inheritance (subclassing) shown with a solid line and filled arrowhead
• Abstract classes and methods shown in italics

Dependency - dashed arrow with open arrowhead

Constraint Rules

Design By Contract and assertions will be used to enforce contraints. This is native to languages like Eiffel. We'll talk more about this later.

Examples: p 31,33,35