[Uml-devel] composition and aggregation associations

Jonathan Riddell jr at jriddell.org
Thu Dec 25 18:17:00 UTC 2003

Oliver has pointed out that we've been doing Composition and
Aggregation associations the wrong way around.

The diamond goes at the owning class, it is not an arrow, which is how
Umbrello has been treating it.


Here MyClass has OtherClass as an attribute.


This is a unidirectional association and MyClass has OtherClass as an

I see that argoUML also has uni-composition and uni-aggregation


I don't think it's part of the standard but it would be good if
someone could confirm that.

I've suggested that Oliver go ahead and change the side that diamonds
are drawn on.  However this is quite a significant change so it should
be well publicised.

On a related note I see that code generation adds all sorts of
accessor methods for Composition but not an actual attribute, this
happens on both sides of the association.  Nothing is added for a
Uni-Association.  Is that the best way to interprit the associtions?


Jonathan Riddell

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