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

Answer 1

An association represents a semantic relationship according to the UML specs.

What is it?

A semantic relationship is a relationship about meanings that has itself a meaning.

This term is borrowed to linguistics and related disciplines, where words are mapped to their meaning, and the relation of words is analysed in view of this mapping. But before getting to abstract, a picture is worth 1000 words:

Semantic relation in UML ?

So, applying this elements of UML (modelling language) instead of English words (natural language): if you'd have the classes Car and Driver, you CAN model the semantic relationship as an association between the two classes.

There can also be a semantic relationship between some Driver and their Spouse meaning that you CAN also model such an association. But this is not mandatory. Fortunately! because otherwise by transitivity you'd quickly have the rest of the world in your model ;-)

If it is relevant for your application domain you may of course show this association as well (e.g. you're working in an insurance company where the prices depends on how many family members have a driving license). And you may even want to make explicit the indirect relation of Spouse and Car, by using the notation for derived association with the leading /.

Semantic or not?

Not all relationships are of semantic nature. You can for example have dependencies, which can express a technical relationship. For example, if you use the factory design pattern, a DriverFactory will «create» the Driver. This has on its own no meaning: It's just a relationship in the domain of the representations. On the other side, you may want to give it a meaning and let the factory keep trace of the drivers created, even if it makes only sense in the meaning of your abstract design and not in the real world. You then CAN make it an association if it helps.

Ultimately, you have a some room for interpretation when you want to see an association and when not. Use it sparsely however, if you want your model to remain helpful.

For the records, I can only draw rectangles, and I'm grateful to this public domain contributor for the nice car and driver and to 18f for its advice on inclusive communication.