[nondet]xref_defined(?Source,
+Goal, ?How)Test if Goal is accessible in Source. If this is
the case, How specifies the reason why the predicate is
accessible. Note that this predicate does not deal with built-in or
global predicates, just locally defined and imported ones. How
is one of of the terms below. Location is one of Line (an integer) or
File:Line if the definition comes from an included (using :-
include(File)) directive.
dynamic(Location)thread_local(Location)multifile(Location)public(Location)local(Location)foreign(Location)constraint(Location)imported(From)