Aggregation and navigability at the same end

Question

In UML, is it possible to draw an aggregation where the component object can access the composite object? Like in this image, but with only one association line, so the asso

Answer 1

Of course that's possible.

If you want to save space, you can use a single line for the association:

Here's my personal opinion about navigability: The navigational arrow is not needed as the existence of the property owner implies that already.

P. 110 of the specs:

When a Property is owned by a Classifier other than an Association via ownedAttribute, then it represents an attribute of the Classifier.

P. 200:

Navigability notation was often used in the past according to an informal convention, whereby non-navigable ends were assumed to be owned by the Association whereas navigable ends were assumed to be owned by the Classifier at the opposite end. This convention is now deprecated. Aggregation type, navigability, and end ownership are separate concepts, each with their own explicit notation. Association ends owned by classes are always navigable, while those owned by associations may be navigable or not.

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But what is an association that is just named? It's a useless construct so far. What you intend is to finally create attributes in either classes - by means of properties in which case you add this (new) dot. To me this is simply over-constructed and impractical. Who is really using those dots? In EA you have to open sub-menus to make them appear. For me (and probably most UML readers) a role name represents a property and this an attribute in the other side. That's just "(my) human logic" behind that proposition. So, my practical approach:

• Use simple connectors for association
• Eventually add (non-) navigability (crosses and) arrows
• Later add role names to indicate the use of attributes at the other end (rather than adding a typed attribute to the class' list).

And that's it. Just forget that silly dot that's a) hard to produce (in EA) and b) even harder to recognize.

Once again: this last part here is my recommendation for practical modeling.