Boolean valued and relational operations
In addition to Boolean valued operations, interval relational operations <, <=, >, >= are useful in decision making. Since intervals are not comparable in binary logic, we have developed fuzzy order relations for intervals to deal with interval valued matrix game and interval weighted graph. I would suggest the committee to consider include fuzzy order relational operations.
References can be found in our recent book "Knowledge Processing with Interval and Soft Computing" (Springer, 2008) pp. 149-152 and 168-172.
Chenyi
> - 4.2 (Boolean valued operations) : comparisons should also mention ==
> and !=.
> Moreover, you mention 3-valued return value, but it may be desirable to
> have
> a 4-valued return value. This is what we did for the C++ proposal where
> interval comparisons return std::bool_set which stands for "true", "false"
> "true or false" and "neither true nor false". In practice, the last value
> is returned when you compare against the empty interval. You get more
> information out of the comparison (the empty interval propagates :) ),
> and there is no significant added cost.