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    In the example you quote the composition is a one-to-many and the aggregation also has a one-to-many relationship implied, though here it could also be a many-to-many relationship for the aggregation (we can suppose possible that a teacher can teach in multiple departments). Whereas a department cannot be part of multiple universities. Composition implies ownership whereas aggregation does not go beyond relationship. The quote is correct but the comment is not. Commented Mar 24, 2011 at 5:20
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    it has nothing to do with destruction! UML does not define garbage collection system. Commented Mar 24, 2011 at 10:01
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    i think the wikipedia link is getting reflexive upvotes, but this is a terrible definition - as @bold pointed out these relationships have nothing to do with GC. This also falls apart when an object is the component of two other objects, such as the ball in a ball-joint joining two artificial limbs. The Component relationship is about functional dependence. Commented Mar 24, 2011 at 14:13
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    I agree that my answer is severely lacking - but so is the WikiPedia article... Commented Mar 24, 2011 at 22:13
  • The difference between composition and aggregation is clear. The problem with aggregation is that it's unclear how it is different from ordinary association. Commented Aug 16, 2016 at 12:20