Source: oose Innovative Informatik eG ( Mr. Axel Scheithauer)
The specification says:
In a Classifier, an attribute may also be shown using association notation, where only an aggregation adornment (hollow or filled diamond) may be shown at the tail of the arrow.
This association-like notation for attributes implies a Multiplicity of * for the opposite end. Since there is no Association and therefore also no opposite end, this Multiplicity can currently not be shown in a diagram. This might be a problem, since most modelers think, that a missing Multiplicity means 1. This is not true, but since this interpretation is so widespread, it should be possible to show the implied Multiplicity, even though there is no model element corresponding to it.
The UML knows many notations that don't directly correspond to a model element (the dashed line between Comment and annotated Element, the circle plus Notation for ownership), so I don't think adding a notation for a virtual Multiplicity poses any problem. It just completes the association like notation. Other distinguishing features are not necessary, because the interpretations are not conflicting: An attribute can also be an associationEnd.
Add following sentence to the paragraph above:
The implied Multiplicity of the opposite end is not limited. A * may may be shown on this end to make it distinguishable from an unidirectional Associaton without defined Multiplicity (which has an implied Multiplicity of 1).
Reported: UML 2.5 — Mon, 28 Aug 2017 18:40 GMT
Updated: Wed, 6 Sep 2017 09:25 GMT