Does a relation (aggregation, composition) replace an attribute?

Question

I\'m pretty new at UML modelling so bear with me.

Say I have a class with an attribute students that is a list of Student instances. I have

Answer 1

An attribute helps to identify the structure of the object. Aggregation gives a high level overview that the object will contain one (or more) of another type. Neither replaces, but instead shows the relationship between the object types.