Negator Functions and Their Companions

If a UDF that returns a BOOLEAN value has a companion function, any user who executes the function must have the Execute privilege on both the function and on its companion. For example, if a function has a negator function, any user who executes the function must have the Execute privilege on both the function and its negator. In addition, the companion function must have the same owner as its negator function.

For information on how to designate a UDF as the companion to its negator function, see NEGATOR.