1. LING/C SC/PSYC 438/538
Lecture 25
Sandiway Fong

2. Today's Topics Homework 12 review 538 Presentations
Grammar transformation: solving left recursive phrase structure

3. Homework 12 Review From Homework 11:
John ate (sensibly) (intransitive eat)
I fish (intransitive fish)
I ate fish (transitive eat)
Bill ate rice
Harry ate roast beef

4. Last Time
g.pl

5. Homework 12 Review
From Ross (1970), English exhibits (forward) gapping:
I ate fish, Bill rice, and Harry roast beef
cf. I ate fish, Bill ate rice, and Harry ate roast beef
Forwards only (cf. Japanese: backwards):
I ate fish, Bill ate rice, and Harry roast beef
*I fish, Bill rice, and Harry ate roast beef
*I fish, Bill ate rice, and Harry ate roast beef (<-NOT gapping)
*I fish, Bill ate rice, and Harry roast beef (<-NOT gapping)
Parallelism requirement:
*I ate fish, Bill, and Harry roast beef
*I ate fish, Bill rice, and Harry

6. Homework 12 Review

7. Homework 12 Review

8. Homework 12 Review Stanford Parser
I ate fish, Bill rice, and Harry roast beef (=2a) (Ross 1970)
Stanford Parser

9. Homework 12 Review
Berkeley Parser:

10. Homework 12 Review
Google AI Blog
Wired magazine

11. Homework 12 Review
I ate fish, Bill rice, and Harry roast beef (=2a) (Ross 1970)
Google (DRAGNN, successor to SyntaxNet)

12. Homework 12 Review I fish, Bill rice, and Harry (fish) beef roast eat
UDPipe:

13. 538 Presentations From the syllabus homeworks: 100% homeworks: 75%
438
homeworks: 100%
538
homeworks: 75%
sub-chapter presentation: 25%
If you are currently taking 438,
and you plan to do the HLT Master's Program
consider volunteering to do the presentation for
a waiver later.

14. 538 Presentations next semester this course continues as 581
We can’t cover as many topics as we’d like this semester
next semester this course continues as 581
Select a topic from some sections from the textbook
not a full chapter
don’t pick something too big or too small …
Range: chapter 14 through 25
you can’t pick the same thing as your classmate
First come, first served basis

15. 538 Presentations Your job: present the selected topic in class
produce slides (send to me first)
you’ll be evaluated on the quality of the presentation
don’t just simply copy the textbook!
important: you'll be evaluated on how well you communicate the essential ideas employed
communicate your understanding of the tradeoffs and limitations etc. be prepared to take questions from me and your fellow classmates

16. 538 Presentations Tuesday: November 27th Thursday: November 29th
Scheduling
Topic selection: begins now
Talk length: 8 mins
first come, first served basis
me your 1st, 2nd and 3rd choices
me your 1st, 2nd and 3rd choice of presentation dates:
Tuesday: November 27th
Thursday: November 29th
Tuesday: December 4th

17. Left recursion and Prolog
Left recursive grammars:
we know from an earlier lecture that left recursive rules are a no-no given Prolog’s left-to-right depth- first computation rule… s a
...
Example:
s --> a, [!].
a --> ba, [a].
a --> a, [a].
ba --> b, [a].
b --> [b].
?- s([b,a,!],[]).
ERROR: Out of local stack
rule for nonterminal a
immediately calls a

18. Preposition Phrase (PP) Attachment
The preferred syntactic analysis is a left recursive parse
Examples:
John saw the boy with a telescope
(structural ambiguity: automatically handled by Prolog)
withinstrument
withpossessive

19. Preposition Phrase (PP) Attachment
The preferred syntactic analysis is a left recursive parse
Can “stack” the PPs:
John saw the boy with a limp with Mary with a telescope
ambiguity: withpossessive , withaccompaniment, withinstrument

20. Preposition Phrase Attachment
Linguistically:
PP (recursively) adjoins to NP or VP
np(np(NP,PP)) --> np(NP), pp(PP).
vp(vp(VP,PP)) --> vp(VP), pp(PP).
Left recursion gives Prolog problems
Derivation (top-down, left-to-right)
sentential forms: vp
vp pp
vp pp pp
vp pp pp pp
vp pp pp pp pp infinite loop…
Note: other extra arguments
not shown here …

21. Transformation Apply the general transformation: to NP and VP rules:
np(np(DT,NN)) --> dt(DT,Number), nn(NN,Number).
np(np(NP,PP)) --> np(NP), pp(PP).
vp(vp(VBD,NP)) --> vbd(VBD), np(NP).
vp(vp(VP,PP)) --> vp(VP), pp(PP).
x(X) --> [z], w(X,x(z)).
x(x(z)) --> [z].
w(W,X) --> [y], w(W,x(X,y)).
w(x(X,y),X) --> [y].
Note:
w is a fresh
non-terminal
that takes 2
arguments
x(x(X,y)) --> x(X), [y].
x(x(z)) --> [z].
[z]
[y] x x
x is the recursive nonterminal
[z]
[y] x x
Let's write some code!