There isn't a negation in SWI-Prolog's tabling. As not/1 takes advantage of a Lower, a person may possibly wind up with incomplete tables and incorrect success. AleksejAleksej 22.9k66 gold badges3636 silver badges3838 bronze badges one Many thanks but my example above is simplified, I really need to use execute https://executive-table-price-phi18494.blogdigy.com/fascination-about-executive-managerial-table-48157845