**Sources:** http://www.omg.org/spec/UML/2.5 (Starting at PDF page 239)
# Associations
An Association classifies a set of tuples representing links between typed instances, e.g., two instances of classes at runtime.
# Aggregation vs Composition
Aggregation and Composition are subsets of associations meaning they are specific cases of association.
In both aggregation and composition object of one class "owns" object of another class. But there is a subtle difference:
* Aggregation implies a relationship where the child can exist independently of the parent. Example: Class (parent) and Student (child). Delete the Class and the Students still exist.
* Composition implies a relationship where the child cannot exist independent of the parent. Example: House (parent) and Room (child). Rooms don't exist separate to a House.
