How can I generate some phrases from a knowledge base after DCG?

Question

I have defined my grammar in prolog as DCG (Definite Clause Grammar). Now I want to generate some phrases according with the facts present in my knowledge base. For example, if I have likes(mark, julia). I want to generate the sentence

Mark likes Julia.

How can I do this?

Answer 1

We must take into account that likes/2 is a normal Prolog predicate, not a DCG.

Hence, we use {}//1 to refer to regular Prolog predicates within DCGs.

For example:

sentence -->
        [X, likes, Y],
        { likes(X, Y) }.

Sample usage:

?- phrase(sentence, Ls).
Ls = [mark, likes, julia].