Prolog CFG

A parser for a very simple subset of English. It is intentionally overly accepting and tries its best to get a parse tree for you.

If it doesn't know a word, it will ask you to supply the word's part of speech. It then learns the word so that next time you run the parser, it remembers what it learned.

References

This grammar was based heavily on the one developed by Michael A. Covington in Natural Language Processing for Prolog Programmers.

Examples

?- use_module(repl).
true.

?- repl.
[DB attached]
Sentence: she looked up the tower
1. s(np(pn(she)),vp(v(looked),pp(p(up),np(d(the),n1(n(tower))))))
2. s(np(pn(she)),vp(v(looked),part(up),np(d(the),n1(n(tower)))))

Sentence: the students challenged the quite unexpected statement at the conference that birds fly
1. s(np(d(the),n1(n(students))),vp(v(challenged),np(d(the),n1(adjp(deg(quite),adj(unexpected)),n1(n(statement))),pp(p(at),np(d(the),n1(n(conference)),s1(comp(that),s(np(d,n1(n(birds))),vp(v(fly)))))))))
2. s(np(d(the),n1(n(students))),vp(v(challenged),np(d(the),n1(adjp(deg(quite),adj(unexpected)),n1(n(statement))),pp(p(at),np(d(the),n1(n(conference)))),s1(comp(that),s(np(d,n1(n(birds))),vp(v(fly)))))))
3. s(np(d(the),n1(n(students))),vp(v(challenged),np(d(the),n1(adjp(deg(quite),adj(unexpected)),n1(n(statement)))),pp(p(at),np(d(the),n1(n(conference)),s1(comp(that),s(np(d,n1(n(birds))),vp(v(fly))))))))
4. s(np(d(the),n1(n(students))),vp(v(challenged),np(d(the),n1(adjp(deg(quite),adj(unexpected)),n1(n(statement))),pp(p(at),np(d(the),n1(n(conference))))),s1(comp(that),s(np(d,n1(n(birds))),vp(v(fly))))))
5. s(np(d(the),n1(n(students))),vp(v(challenged),np(d(the),n1(adjp(deg(quite),adj(unexpected)),n1(n(statement)))),pp(p(at),np(d(the),n1(n(conference)))),s1(comp(that),s(np(d,n1(n(birds))),vp(v(fly))))))

Sentence: harold slept soundly
These words are unknown: [harold,soundly]
-  harold
    Part-of-speech tags: [determiner,degree,adjective,noun,preposition,pronoun,name,complementizer,verb,particle,adverb,conjunction]
    Enter part of speech (followed by '.'): name.
-  soundly
    Part-of-speech tags: [determiner,degree,adjective,noun,preposition,pronoun,name,complementizer,verb,particle,adverb,conjunction]
    Enter part of speech (followed by '.'): |: adverb.
1. s(np(nm(harold)),vp(v(slept),advp(adv(soundly))))

Sentence: Could not parse
Sentence: quit
Quitting...
[DB detached]
false.

Project Organization

The grammar is specified in syntax.pl.

The ++> operator is defined in plus_plus_arrow.pl.

The database of known words is stored in _data.pl, and its public interface is defined in data.pl.