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**Sources:** http://www.omg.org/spec/UML/2.5 (Starting at PDF page 239)
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# Associations
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An Association classifies a set of tuples representing links between typed instances, e.g., two instances of classes at runtime.
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# Aggregation vs Composition
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Aggregation and Composition are subsets of associations meaning they are specific cases of association.
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In both aggregation and composition object of one class "owns" object of another class. But there is a subtle difference:
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* 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.
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* 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.
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