This operator is represented by the keyword "xor". It is used to express an exclusive or relationship between two Boolean expressions. The expression "a xor b" is true if either a is true and b is false, or a is false and b is true. If both a and b are true or both are false, the expression is false. For example, "I will either go to the beach (a) or go hiking (b), but not both" can be expressed as "a xor b" in OCL.