Sandiway Fong Lecture 12 Adminstrivia Review Homework 4 on Recursion Continue on with the left to right recursion grammar transformation Last Time abstract grammar fragment Today PP adjunction to NP and VP ID: 352061
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Slide1
LING 388: Language and Computers
Sandiway
Fong
Lecture 12Slide2
Adminstrivia
Review:
Homework 4 on Recursion
Continue on with the left to right recursion grammar transformation:
Last Time: abstract grammar fragment
Today: PP adjunction to NP and VPSlide3
Homework 4 Review
Recursion type 1:
w
e can stack adjectives…
the bus
the big busthe big red busthe shiny big red bus(cf. the big shiny red bus)
Recursive rule:right recursive rulenn --> a, nn.Slide4
Homework 4 Review
Start with
grammar.pl
from the course webpage:
nn
(nn(A,NN)) --> a(A), nn(NN).
a(jj(big)) --> [big].a(jj(shiny)
) -->
[shiny]
.a(jj(red)) --> [red].nn(nn(bus)) --> [bus].
sentence(s(X,Y)) --> np(X), vp(Y).
pp
(
pp
(X,Y)) --> in(X),
np
(Y).
in(in(with)) --> [with].
np
(
np
(X)) -->
prp
(X).
np
(
np
(
np
(X,Y),Z)) --> det(X),
nn
(Y),
pp
(Z).
np
(
np
(D,NN)) --> det(D),
nn
(NN).
prp
(
prp
(i)) --> [i].
prp
(
prp
(
me
)) --> [
me
].
nn
(
nn
(boy)) --> [boy].
nn
(
nn
(
telescope
)) --> [
telescope
].
vp
(
vp
(V,X)) --> verb(V),
np
(
X
).
vp
(
vp
(V,X,Y)) --> verb(V),
np
(
X
),
pp
(Y).
verb
(
vbd
(
saw
)) --> [
saw
].
det
(
dt
(the)) --> [the].
det
(
dt
(a)) --> [a].Slide5
Homework 4 Review
Tree representation:Slide6
Homework 4 Review
Tree representation:Slide7
Homework 4 Review
Tree representation:Slide8
Homework 4 Review
Tree representation:Slide9
Homework 4 review
Recursion is a property of natural language
s
imple iteration: …
big shiny red bus
Another kind of recursionSome verbs can select for clauses (as well as object NPs), e.g. noticeI noticed that John noticed that Mary noticed the big red bus[S I noticed [SBAR that [S John noticed [SBAR that [S Mary noticed the big red bus]]]]]
Idea: some verbs can select for sentences introduced by the complementizer thatSlide10
Homework 4 review
Example:
Mary noticed the big red bus
verb(
vbd
(noticed)) --> [noticed].np(
np(X)) --> proper_noun(X).proper_noun(nnp(
mary
)) --> [
mary].Slide11
Homework
4
review
Example:
John noticed that Mary noticed the big red bus
vp
(vp(V,SBAR)) -->
verb(
V),
sbar(SBAR).sbar(sbar(C,S)) --> c(C), sentence(S).c(c(that)) --> [that].proper_noun
(
nnp
(john))
--> [john]
.
(IN that)Slide12
Homework 4 review
Example:
I noticed that John
noticed that Mary
noticed the big red busSlide13
Homework 4 review
Example:
I noticed that John noticed that Mary noticed the big red busSlide14
Today’s Topic
Exercise:
Convert left recursive natural language grammar rules into right recursive grammar rulesSlide15
Step 1
Recipe:
Let
x
be the nonterminal with the left recursion.
Let z be the terminal (or nonterminal) sequence that x also expands toLet y be the terminal (and/or nonterminal) sequence after the left recursive callAbstract example from last time:x --> x, [y].x --> [z].Slide16
Step 1
Part 1:
identify x, y, and z in the following rules:
np
-->
dt, nn.np --> np, pp.identify x, y, and z in the following rules:
vp --> vbd, np.
vp
-->
vp, pp.x --> x, [y].x --> [z].Slide17
Step 2
Transformation:
x --> x, [y].
x --> [z].
into
x --> [z], v.v --> [y], v.v --> [y].x --> [z].Step 2:apply transformation to: np --> dt
, nn. np --> np, pp.
also to:
vp --> vbd, np. vp --> vp, pp.Slide18
Step 3
Step 3:
modify the grammar fragments from step 2 into grammars that compute parse trees
test your grammar fragments on VPs like
saw a boy with a telescope
vp(Parse,[saw, a, boy, with, a, telescope], []).Abstract example:x --> [z], v.v --> [y], v.v --> [y].x --> [z].modified version:
x(x(z,V)) --> [z], v(V).v(v(y,V)) --> [y], v(V).v(v(y)) --> [y].x(x(z)) --> [z].Slide19
Comparison
“Quick Fix” grammar from last time:
Result:Slide20
Step 4
Step 4:
Compare the transformed grammar parses with those obtained using the “Quick Fix” grammar on the NP
a
boy with a telescope with a limp
number of parses?attachment of the PPs?