UML: Bi-directional and Multiplicity

Question

What is the notation for multiplicity when there isa bidirectional relationship? Are we supposed to list the multiplicity twice for at each arrow?

Answer 1

Multiplicity does not depend on navigation (I assume that by bidirectional you are referring to the navigability of the associations). They are two independent properties. So, yes, multiplicities must be indicated for each end of the relationship

Answer 2

Graphical notation of an association does not have arrows at the end of the association links. Some tools such as eUML or others are adding arrows at the end but this is not a valid UML notation.

If the association is navigable in just one side then you need an arrow at one of the end.