UMLR — Missing constraints for class Interval

There should be at least two invariant constraints here:

1. The types of "min" and "max" should be the same, and for both "min" and "max" the operation "isComputable()" should return "true";
2. The value of "min" must be less than or equal to that of "max".

A third such constraint could be added that the type(s) must not be Null.