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LING 388: Language and Computers. Sandiway Fong 10/17 Lecture 16. Administrivia. Extra Credit Homework 5 Due tonight. Complexity of PP attachment. Last time…. d on’t store the actual parses. Complexity of PP attachment. Computed up to nearly 97 million parses!. Today’s Topics.

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Ling 388 language and computers

LING 388: Language and Computers

Sandiway Fong

10/17

Lecture 16


Administrivia
Administrivia

  • Extra Credit Homework 5

    • Due tonight


Complexity of pp attachment
Complexity of PP attachment

Last time…

don’t store the actual parses


Complexity of pp attachment1
Complexity of PP attachment

Computed up

to nearly

97 million

parses!


Today s topics
Today’s Topics

  • Homework 4 Review


Homework 4 review
Homework 4 Review

  • Part 1: construct a grammar for the sentences:

    • I want John to win

    • I want to win

    • I want John to win the race

    • I want to win the race


Homework 4 review1
Homework 4 Review

Start

with

hw4.pl



Homework 4 review3
Homework 4 Review

  • Need to add rules for:

    • infinitival clause (“to”)

    • “want” to select for an infinitival clause complement

    • verb “win” to optionally take an NP complement

    • subject of infinitival clause can be empty (PRO)


Homework 4 review4
Homework 4 Review

  • Need to add rules for:

    • infinitival clause (“to”)

vp(vp(VBP,S)) --> vbp(VBP), s(S).

vbp(vbp(want)) --> [want].

But we already have an s rule for finite clauses:

s(s(NP,VP)) --> np(NP), vp(VP).

And we would like “want” to select for an infinitival s

Solution is to copy and rename…

vp(vp(VBP,S)) --> vbp(VBP), s_inf(S).

vbp(vbp(want)) --> [want].

s_inf(s(NP,VP)) --> np(NP), vp_inf(VP).

vp_inf(vp(TO,VP)) --> to(TO), vp_inf(VP).

to(to(to)) --> [to].

vp_inf(vp(VB)) --> vb(VB).

vb(vb(win)) --> [win].


Homework 4 review5
Homework 4 Review

  • Rules added so far:

even when NN “race” is added


Homework 4 review6
Homework 4 Review

  • Rules added so far:

allow VB to optionally take an object


Homework 4 review7
Homework 4 Review

  • Rules added so far:

problem is here


Homework 4 review8
Homework 4 Review

  • Rules added so far:

allow empty

subject

copy and modify rule


Homework 4 review9
Homework 4 Review

  • BTW, rules given are not perfect; e.g. vp_inf recursion is too permissive:


Homework 4 review10
Homework 4 Review

  • Part 2: Compare the sentences in part 1 with:

    • I trust John to win

    • *I trust to win

    • I trust John to win the race

    • *I trust to win the race

    • Modify your grammar from part 1 to handle part 2 as well, i.e. it should accept and reject accordingly


Homework 4 review11
Homework 4 Review

  • If we simply add trust as vbp, it’ll pattern exactly like want:

but we wanna block

these two parses


Homework 4 review12
Homework 4 Review

  • Generalization:

    • want takes s_inf with overt and empty NP subjects

    • trust takes s_inf with overt NP subjects only

  • There are two s_inf rules. One encodes overt and the other empty subjects. Split them up into s_inf1 and s_inf2:

1

2


Homework 4 review13
Homework 4 Review

  • Let vbp1 select for s_inf1 and vbp2 for s_infl2, respectively. Then want is both a vbp1 and vbp2 verb. And trust is only vbp1:


Homework 4 review14
Homework 4 Review

  • Let’s make sure want still works…


Homework 4 review15
Homework 4 Review

  • Summary:

    • This is a construction-specific approach

    • There are two s infinitival constructions:

      • [Sinf1 NP [VPinf to [VPinf [VB win] .. ]]]

      • [Sinf2 [NP ∅] [VPinf to [VPinf [VB win] .. ]]]

    • want selects for 1. and 2.

    • trust selects for 1. only

We restrict the scope of the grammar rules by selective copy

and renaming

A GB-theoretic approach might say: want optionally assigns exceptional Case

and trust obligatorily assigns exceptional Case to the subject of its complement.

In an infinitival clause, a subject does not normally get Case.

Overt NPs must get Case.

[NP∅] (aka PRO) cannot receive Case.


G16 pl
g16.pl

  • We now have built quite a complex little grammar so far in this course …

    • use this grammar for today’s exercise

    • download from the website

    • it’s about 50 rules, organized into sections by phrase type…






G16 pl5
g16.pl

  • Note:

    • g16.pl could but it doesn’t incorporate the PP attachment rules from the previous lecture …


Exercise 1
Exercise 1

  • Determiner-Noun Agreement

  • example

    • English determiner-noun number agreement

    • data

      • the man

      • the men

      • a man

      • *a men

    • lexical features

      • man [singular]

      • men [plural]

Like in the case of want vs. trust:

the [singular] want vbp1

the [plural] want vbp2

a [singular] trust vbp1


Exercise 11
Exercise 1

  • Method 1: nonterminal renaming

    • rename grammar rules to constrain the possibilities for determiner and noun co-occurrence:

dt_singular(dt(a)) --> [a].

dt_plural(dt(the)) --> [the].

dt_singular(dt(the)) --> [the].

  • write lexical rules for man/men:

nn_singular(nn(man)) --> [man].

nn_plural(nn(men)) --> [men].


Exercise 12
Exercise 1

  • Method 1: nonterminal renaming

    • rename grammar rules to constrain the possibilities for determiner and noun co-occurrence:

  • rewrite existing rules involving nn and dt


Exercise 13
Exercise 1

  • Need to also rename other lexical rules:

How should we handle cheese?


Exercise 2
Exercise 2

  • Method 2: use an extra argument to hold a variable corresponding to the Number feature

    e.g. dt(D,Number), nn(N,Number)

    then the value of the variable Number must match for determiner and noun

    • the [plural/singular]

    • a [singular]

    • man [singular]

    • men [plural]


Exercise 21
Exercise 2

  • Lexical rules for determiners and nouns must now define the value of Number as a 2nd argument as well

  • e.g.

    • nn(nn(man),singular) --> [man].

    • dt(dt(a),singular) --> [a].

  • download g16.pl again and implement this system

  • Which way is better?