associations - Semantic relationship in UML

Question

I found a definition for association in UML as below. An "association" in UML is defined as a kind of relationship between classes,which represents the semantic relationship between two or more classes that involves connections (links) among their instances .

I am not clear what is semantic relationship. Can anyone explain it with example with comparing it with non semantic relationship?

Answer 1

The subject of Semantics is sense. If one thing has something that is connected by sense to another thing, it is the semantic relationship. That definition is terribly wide. And, applied to UML relationship, incorrect. It is incorrect for two reasons.

First, UML covers not only Class-Instance languages, such as Java or C++, but pure object languages with heredity created by Prototypes as well. And this second variant is not covered by your definition at all.

Second, in UML you can have class A connected to class B through some complex AssociationClass, that is shown by a box with arrows, not arrow only. And it still will be named an association and it IS a semantic relationship, too. But a the semantic relationship goes from A to B through two classes, it is still a semantic relationship, but it is not an association in UML.

If you are trying to be deep in subject, better read the UML documentation: "An Association classifies a set of tuples representing links between typed instances." (UML 2.5, pharagraph 11.5.1). Notice: ANY link between two instances can be shown as an association. Maybe the book you are reading is wholely not so bad, but in the very place that you have cited the author merely tries to use pretty words not understanding their meaning and not even trying to be understandable to readers and to be CORRECT.