UML Class Diagram Relationships and Symbols

1. Inheritance  

B inherits from A.

2. Realization

B implements A.

3. Association

A and B call and access each other’s elements.

4. Association (one way)

A can call and access B’s elements, but not vice versa.

5. Aggregation

A has a B, and B can outlive A.

6. Composition

A has a B, and B depends on A.