Standard predicates are always available to the Prolog interpreter, and do not need to be imported or loaded explicitly as do other Prolog predicates. Our standard predicates are listed below. Standard predicates whose semantics depend on HiLog terms or on SLG evaluation are marked as HiLog or Tabling.
It is possible for the user to add standard predicates not provided in the standard release. See the section on Customizing XSB.