What is Navigability in UML diagrams?

Question

What is an example of Navigability in UML diagrams? My professor has provided the follow figure, but I can\'t seem to figure it out:

Answer 1

The UML specs is an intricate pile of alternative notations that can drive you crazy. Explore with caution!

In real life, KEEP IT SIMPLE! Don't use "dot notation" and don't use x to denote non-navigability, unless your peers are familiar with it.

Use arrows for navigable associations. People are familiar with it, or if not they're intuitive enough.