Harini's Tabling Demo

 
/* File:   Superior.P
** Author: Harini Rao
**
** Tabling is one of the two ways of evaluating predicates in XSB. In tabling, 
the implementation keeps track of all calls to tabled predicates, or tabled 
subgoals. Whenever a new tabled subgoal  is called, a check is first made to 
see whether it is in the table. If so, the subgoal is resolved against answers 
in the table;
**
** If not, it is entered into the table and resolved against program clauses. 
When an answer to a tabled subgoal is derived, a check is made against the table
for to see if the answer is there. If the answer is not in the table, the 
answer is added and scheduled to be returned to all instances where  has been 
called;
**
** If the answer is already in the table, the evaluation simply fails and 
backtracks to generate more answers. 
**
*/



:- table superior/2.
    superior(X,Y) :- supervise(X,Y).
    superior(X,Y) :-	supervise(X,Z), superior(Z,Y).

supervise(jennifer,ahmad).
supervise(james,jennifer).
supervise(franklin,john).
supervise(franklin,ramesh).
supervise(franklin,joyce).
supervise(jennifer,alicia).
supervise(james,jennifer).
supervise(james,franklin).