UML class model how to model many to many relationship

Question

I have read several tutorials on what a UML model should contain and what not. As a developer I always think in terms of a relational data model where you could never have a many to many relationship between tables. Now with a UML class model, I've read that if they don't provide added value, you could just skip the linktables.

However I've also read a tutorial where examples where given using data inside tables and was strongly suggesting to picture each class as a simple table while modeling your class model.

I am confused, what is it now?!

Answer 1

Model it as an M:N relationship. Same as in a relationship model there will be an associate class (or link class) of some kind in code. No need to put that on the diagram unless it has attributes on top of the join attributes (much like you would generally omit a join entity from an ERD unless it had attributes that weren't foreign keys in the related entities). The link class is typically drawn as a class connected to the relationship by a dashed line.

The Enrolment join entity is a good example of this in UML 2 Class Diagrams.