Solution is a solution of Puzzle, where Puzzle is puzzle(Clues,Queries,Solution).

Source: The Art of Prolog

Program source code: puzzle.pl

	/* Test data */
 
	test_puzzle(Name,Solution) :-
		structure(Name,Structure),
		clues(Name,Structure,Clues),
		queries(Name,Structure,Queries,Solution),
		solve_puzzle(puzzle(Clues,Queries,Solution),Solution).
 
	structure(test,[friend(N1,C1,S1), friend(N2,C2,S2), friend(N3,C3,S3)]).
 
	clues(test,Friends,
		[(did_better(Man1Clue1, Man2Clue1, Friends),		% Clue 1
		  name_(Man1Clue1, michael), sport(Man1Clue1,basketball),
		  nationality(Man2Clue1,american)),
		 (did_better(Man1Clue2, Man2Clue2, Friends),		% Clue 2
		  name_(Man1Clue2, simon), nationality(Man1Clue2,israeli),
		  sport(Man2Clue2,tennis)),
		 (first(Friends,ManClue3),sport(ManClue3,cricket))
		]).
 
	queries(test, Friends,
	    [ member(Q1,Friends),
			name_(Q1,Name),
			nationality(Q1,australian),                     % Query 1
			member(Q2,Friends),
			name_(Q2,richard),
			sport(Q2,Sport)							        % Query 2
		],
		[['The Australian is', Name], ['Richard plays ', Sport]]
	).
 
	did_better(A,B,[A,B,C]).
	did_better(A,C,[A,B,C]).
	did_better(B,C,[A,B,C]).
 
	name_(friend(A,B,C),A).
	nationality(friend(A,B,C),B).
	sport(friend(A,B,C),C).
 
	first([X|Xs],X).
/*
	solve_puzzle(Puzzle,Solution) :-
		Solution is a solution of Puzzle,
		where Puzzle is puzzle(Clues,Queries,Solution).
*/
 
	solve_puzzle(puzzle(Clues,Queries,Solution),Solution) :-
		solve(Clues),
		solve(Queries).
 
	solve([Clue|Clues]) :-
		Clue, solve(Clues).
	solve([]).
 
%	Program 14.6: A puzzle solver
 
%?-test_puzzle(test,Solution).