How does the {XOR} constraint work in UML?

Question

I have some doubts about the correct use of the {XOR} constraint in UML.

I understand how this works in two different ways. Which one is correct?

• The xor constraint applies to associations. (either: an object of type A can be associated with 1 object of type C, or: an object of type A can be associated with zero or one object with type B or: an object A can only be on its own, because we have [0 .. 1] near B).

• The xor constraint applies to the link (either: an object of type A must be associated with only one object of type C, or: an object of type A must be associated with only one object of type B),

Answer 1

( ). A C. - XOR B. : B 0, .

(!) - . , . , A, B, C, .

Answer 2

2 B.

1 :

• 1 A, 0..1 B
• 0..1 A, 0..1 B
• 0..1 A, 1 B