UML Course
Multiplicity
Since the relationship between two classes is defined by an association, we are simply adding the multiplicity's value to it.
You should read here that
- m is a value representing the number of instances of the class A interacting with an object of the class B
- n is a value representing the number of instances of the class B interacting with an object of the class A
And, yeah, the number is on the opposite side.
Notice that the value is at the opposite side. The values that we can use are
- n: exactly n, this is a number like 0,1,2,...
- *: 0 or more
- 0..1: 0 or 1
- 0..*: same as *
- 1..*: 1 or more
- n..*: n or more
- n..m: at least n, and up to m
- n..n: same as n
For instance, in the example above with n..m, we could replace our n by 0..1 (0 or 1) and our m by * (0 or more).