UML aggregation vs association

Question

Here I am, with another question about aggregation and association. I wanted to learn some basics of UML, so I started reading \"UML distilled\" by Martin Fowler. I read bot

Answer 1

Implementation wise there is not much of a difference but conceptually there is big difference: aggregations are used to express a hierarchy. When you work with a hierarchy of components there are certain type of operations you need to have in the root interface:

• find subcomponents in the hierarchy
• add/remove subcomponents to/from the hierarchy
• change common attributes of all components
• traverse the hierarchy recursively (Visitor pattern)
• reconfigure the hierarchy and the links (associations) between the components

Most of these operations are not needed when dealing with associations.