5.3.5 Questions

As we have promised above, we now apply the technique of gap threading to another phenomenon: wh-questions.

As we have promised above, we now apply the technique of gap threading to another phenomenon: wh-questions. Let us look at an example:

• ``Harry likes the witch.''

• ``Who likes the witch?''

So we can think of this wh-question as a sentence with a gap:

If we want to ask about the witch, not about Harry, we form the following question:

So this looks very much like the analysis of relative clauses that we had in the previous paragraph, except for one small complication: When we ask about the object, we have to use an auxiliary and the infinite form of the verb (``does...like''). Apart from that, the heart of the new DCG (found in dCG4Questions.pl ) contains nothing really new:

%subject interrogative

s(F-F) --> wh, vp(F-F,fin).

%object interrogative

s(F-F) --> wh, aux, np(F-F), vp([gap(np)|F]-F, inf).

vp(F-G, FIN) --> v(1, FIN),np(F-G).

vp(F-G, FIN) --> v(2, FIN),np(F-H),pp(H-G).

Auxiliary and a wh-pronouns are added to the lexicon straight forward:

% auxiliary

aux --> [does].

% wh-pronoun

wh --> [who].

The annotation of verbs as being finite or not is achieved by adding a new feature:

v(1,inf) --> [like].

v(1,fin) --> [likes].

...

Finally, we have said that relative constructions are a case of unbounded dependencies: an arbitrary amount of material may stand between the gap and the extracted and moved noun phrase. The same holds for wh-questions: From a sentence like ``Harry said that a witch likes Ron.'' we can get to the question

And of course we can make the question even longer, for example like this: