A DCG handling the syntax and meaning of a small subset of natural language.

Source: PROLOG programming for artificial intelligence, 3rd Edition, Harlow, 2001, ISBN 0-201-40375-7.

Program source code: dcg.pl

%  Figure 17.6  A DCG handling the syntax and meaning of a small
%  subset of natural language.
 
 
:-  op( 100, xfy, and).
:-  op( 150, xfy, =>).
 
sentence( S)  -->
  noun_phrase( X, P, S), verb_phrase( X, P).
 
noun_phrase( X, P, S)  -->
  determiner( X, P12, P, S), noun( X, P1), rel_clause( X, P1, P12).
 
noun_phrase( X, P, P)  -->
  proper_noun( X).
 
verb_phrase( X, P)  -->
  trans_verb( X, Y, P1), noun_phrase( Y, P1, P).
 
verb_phrase( X, P)  -->
  intrans_verb( X, P).
 
rel_clause( X, P1, P1 and P2)  -->
  [that], verb_phrase( X, P2).
 
rel_clause( X, P1, P1)  --> [].
 
determiner( X, P1, P, all( X, P1 => P))  --> [every].
 
determiner( X, P1, P, exists( X, P1 and P)) --> [a].
 
noun( X, man(X))  -->  [man].
 
noun( X, woman(X))  -->  [woman].
 
proper_noun( john)  -->  [john].
 
proper_noun( annie)  -->  [annie].
 
proper_noun( monet)  -->  [monet].
 
trans_verb( X, Y, likes( X, Y))  -->  [ likes].
 
trans_verb( X, Y, admires( X, Y))  -->  [admires].
 
intrans_verb( X, paints(X))  -->  [paints].
 
% Some tests
 
test1( M)  :-
  sentence( M, [john,paints],[]).
 
test2( M)  :-
  sentence( M, [a, man, paints], []).
 
test3( M)  :-
  sentence( M, [every,man,that,paints,admires,monet],[]).
 
test4( M)  :-
  sentence( M, [annie,admires,every,man,that,paints],[]).
 
test5( M)  :-
  sentence( M, [every,woman,that,admires,a,man,that,paints,likes,monet],[]).