Parsing Homework 3
Name:
Chapter 13 of your textbook primarily covers this material.
1. The following sentence has a prepositional phrase attachment ambiguity. Draw two parse trees that attach the
ambiguity in two different locations: He dropped the ball with his right hand.
(another question! flip page over!)
2.
CKY Algorithm
Below is a probabilistic CFG and a 5-word sentence. Fill in the CKY table using the provided PCFG. Each cell
should contain any matching non-terminals, and each non-terminal must have the probability of that nonterminal’s subtree. The first cell is filled in for you.
Grammar Rules
S → NP VP
VP → VP PP
VP → V V
VP → VP RB
NP → DT NP
NP → J N
NP → N
1.0
0.7
0.2
0.1
0.6
0.2
0.2
Lexicon (doesn’t show all words, so doesn’t sum to 1.0)
DT → the
0.6
RB → quickly
0.4
V → has
0.1
V → arrived
0.2
V → fall
0.1
N → fall
0.2
“The fall has arrived quickly”
0
1
2
3
4
5
(0,1)
(1,2)
(2,3)
(3,4)
(4,5)