CSCI 587 - Lecture 17 Parsing wh-Questions

• I have to follow him. Have not aux here!
• modals can never follow have or be, since they have no past-participle
• MAIN feature: binary + for main-verbs, - for auxs
• PASS(passive feature): VP -> AUX[be] VP[pastptr, main]
• subject-aux inversion
• Lexicon for auxiliary verbs (fig 5.2)
• Movement in Language
  • local movement - subject-aux inversion
  • unbounded movement -

     
            Sam found the old bicycle in the basement.
            What did Sam find in the basement?
            Where did Sam find the bicycle?
            How did Sam find the bicycle?
            Who found the old bicycle in the basement?        

  • Types of movement (Box 5.2)
• wh-questions: what, who, when, where, how,
• More complex variations

   
          In what part of the basement did Sam find the bicycle?
          Under what circumstances can I pass this course?
          

• Gap - the place where a subconstituent is missing
• filler
• Dealing with movement
  • Chomsky's Transformational Grammars (Box 5.1)
  • ATN: hold list and Virtual arcs (figure 5.14***)
  • slash categories: X/Y an X with a Y missing
  • GAP Feature: S/NP == S[GAP NP]
• Restrictions on Movements

  The man who was holding the two balloons will put the box in the corner.
  *What will the man who was holding _ put the box in the corner?

• Extending grammar 4.7 to handle Questions in CFGs
  S[+inv] -> (AUX AGR ?a SUBCAT ?v) (NP AGR ?a)(VP VFORM ?v)
• To handle wh-questions you need to add the GAP feature
• GAP feature passed from mother until the correct place is found
• Rules to allow insertion in the correct place
  (NP GAP ((CAT NP)(AGR ?a)) AGR ?a) -> empty
• passing the GAP feature
• If the head is non-lexical then the GAP is only passed to the Head
  (S GAP ?g) -> (NP GAP -)(VP GAP ?g)
• If the head is lexical then the GAP can be passed to any subconstituent
  VP -> V[_np_vp:inf] NP PP
  adding GAP results in two new rules
  (VPGAP ?g) -> V[_np_vp:inf] (NPGAP ?g) (PPGAP -)
  (VPGAP ?g) -> V[_np_vp:inf] (NPGAP -) (PPGAP ?g)
• WH feature - indicates the type of WH: Q(question) or R (relative clause)
• Examples of various CAT feature for wh-words
• Lexicon for wh-words (fig 5.6)
• Extending grammar to handle wh-words
• Parsing with Gaps
• Empty Constituent Insertion Algorithm
• Movement Constraints
  • The A over A constraint
  • Complex-NP constraint (relative clause)
  • Sentential Subject constraint
  • Wh-Island constraint
  • Coordinate Structure constraint

Readings

Sections 5.2-5.3

Assignment 6

1. p 154 #1,
2. p 154 #2,
3. Extend nlp4 to include the feature AGR.
4. Extend nlp4 to handle Yes/No questions, including the features AGR, VFORM>, SUBCAT>, COMPFORM> (but explicitly not requiring GAP and WH).

Reminder

Test 2 April 10