Download Semantics III: Parsing, logical form, abduction

CS 544: Lecture 3.3
Syntax and Compositional
Semantics
Jerry R. Hobbs
USC/ISI
Marina del Rey, CA
Lexicon and Syntax
S
Syntax tells us
identity of arguments
x1=x2
NP
John
john’(e1,x1)
The lexicon gives us
the predicates, one
for each word/morpheme
e1 is the property of x1 being John
e2 is the event of x2 working
e3 is the property of e2 being in the present
VP
works.
work’(e2,x2) & Present’(e3,e2)
Syntax is how we
get predicate-argument
structure out of
concatenation
All the Syntax of English (almost)
Structure of the clause
Structure of the noun phrase
Adverbials
Relative clauses and other long-distance
dependencies
Conjunctions (or Coordination)
Structure of the Clause
The basic clause consists of a Subject, a Verb, and zero, one or two
Complements.
Chris sleeps. Chris helps Pat. Chris gave Pat a book.
The Complements can be NPs, PPs, AdjPs or clauses, e.g.,
PP: Chris relies on Pat.
AdjP: Chris is acting foolish.
Infinitive: Chris wants to fly. Chris wants Pat to fly.
Full declarative clause: Chris knows that he can’t fly.
Gerunds: Chris likes seeing movies.
Small clauses: Pat considers Chris foolish.
Sometimes the subject of the main clause becomes the subject
of the complement as well.
Chris wants to fly ==> want’(e1,C,e2) & fly’(e2,C)
(Subject Control)
Subcategorization is the specification for each verb of the kinds
of complements it can take:
want: NP, Infinitive, NP Infinitive
Auxilliaries
Auxilliaries are
subject control verbs,
subcategorized
for the kind of VP
that can follow them.
It could have been fixed by now.
VP
could
Modal, subcategorized
for tenseless VP
“have” conveys Perfect;
subcat VP[vbn]
“be” + VP[vbn]
conveys passive;
subject moves to
object position
VP
have
been
VP
VP
fixed
could’(e1,x,e2) & Perfect’(e2,e3) & fix’(e4,y,x)
Prepositions and Adjectives
Also Subcategorize
Prepositions:
NP: in the room
Declarative clause: Before the party was over, Chris left.
Small clause: With the party dying down, Chris left.
(subordinate conjunctions)
Adjectives:
Infinitive: able to fly
“that” clause: certain that he could fly
Predicate Complements
Complements of the verb “be”:
NP: Chris is a computer scientist.
PP: Chris is in this building.
AdjP: Chris is able to ski.
be’(e,x,y)
in’(e,x,y)
able’(e,x,e1) & ski’(e1,x)
Present and past participles can appear anywhere
adjectives can appear.
Similarly, VP[vbg], VP[vbn] for AdjP
VP[vbn]: Chris was given a book. (passive)
VP[vbg]: Chris is reading the book. (progressive)
All the Syntax of English (almost)
Structure of the clause
Structure of the noun phrase
Adverbials
Relative clauses and other long-distance
dependencies
Conjunctions (or Coordination)
Structure of NPs: Left Modifiers
all the many tall educated Washington presidential foreign policy advisors
Head noun: advisor’(e0,x)
& Plural’(e1,x,s)
Prenominal nouns: Washington’(e2,w) & nn’(e3,w,x)
Also noun-like Adjs: president’(e3,y) & nn’(e4,y,x)
Adjectives: tall’(e5,x)
Also vbn, vbg: educate’(e6,z,x)
Quantifiers, Numbers: many’(e7,s) (property of the set in plurals)
Determiner: the’(e8,x, ....&e1)
(relation between entity x and description given by rest of NP)
Possessive NPs are determiner phrases: Amy’s => pos’(e10,a,x)
Predeterminer: all’(e9, s, ...&e1)
IN THIS ORDER
(relation between set and description)
Some Ambiguities
Often a word can be an adjective in the adjective position:
criminal lawyer: a lawyer who is a criminal
Or a noun in the prenominal noun position:
criminal lawyer: a lawyer who bears some relation to
criminals, i.e., defends them
A present participle of a verb can appear in both places:
a skiing man vs. a skiing lesson
noun position: lesson w some relaion to skiing
adjective position: a man who is skiing
The Structure of NPs:
Right Modifiers
Anything that can be a predicate complement can be the right
modifier of a noun:
NP: the artist Michelangelo; George Bush, president of the U.S.
(appositives)
be’(e1,a,m)
PP: the man in the black coat, the party after Chris was elected
after’(e1,p,e2)
AdjP: the people responsible for the damage responsible’(e1,p,d)
VP[vbn]: the student given a present
give’(e1,x,s,p)
VP[vbg]: the people seeing the movie
see’(e1,p,m)
The head noun is the “subject” of the predicate.
Also relative clauses:
the people that Chris saw () yesterday.
The head noun fills the gap.
see’(e1,c,p)
All the Syntax of English (almost)
Structure of the clause
Structure of the noun phrase
Adverbials
Relative clauses and other long-distance
dependencies
Conjunctions (or Coordination)
Structure of Adverbials
read’(e2,c,b)
Anything that can be a predicate complement can also be
an adverbial:
in’(e1,e2,l)
enthusiastic’(e1,c,s)
PP: Chris read the book in the library.
AdjP: Chris read the book, enthusiastic about the subject.
be’(e1,e2,s)
NP: Chris read the book, a real surprise to me.
VP[vbn]: Chris read the book, based on what Pat told me. base’(e1,x,e2,e3)
VP[vbg]: Chris read the book, wishing he didn’t have to.
wish’(e1,c,e3)
Also adverbs:
Chris read the book quickly.
quick’(e1,e2)
Also relative clauses:
Chris read the book, which surprised me.
surprise’(e1,e2,i)
Placement and Logical Form
of Adverbials
Adverbials can appear before, after or between any of the
constituents of the structure it modifies.
Quickly Chris read the book.
Chris quickly read the book.
Chris read quickly every book that was required.
Chris read the book quickly.
The “subject” of the adverbial is the eventuality associated
with the S or VP it modifies:
Chris read the book in the library.
read’(e1,c,b) & in’(e2,e1,l)
Chris read the book quickly.
read’(e1,c,b) & quick’(e2,e1)
Argument or Adverbial?
For PPs especially, it is often unclear whether it is
and argument or adverbial:
Pat will go from California to Japan.
==> go’(e,p,c,j) OR go’(e,p) & from’(e1,e,c) & to’(e2,e,j)
In an inference system with the right rules, this distinction
doesn’t matter:
go3’(e,x,y,z) <--> go1’(e,x) & from’(e1,e,y) & to’(e2,e,z)
All the Syntax of English (almost)
Structure of the clause
Structure of the noun phrase
Adverbials
Relative clauses and other long-distance
dependencies
Conjunctions (or Coordination)
Long-Distance Dependencies
(including wh-Constructions)
filler
gap
Relative clauses, used as right modifiers of nouns (and Ss):
Don’t bite the hand that () feeds you.
Chris visited the town where he was born.
Chris left early, which () surprised us.
Wh-Questions:
What did Chris see ()?
Where did Chris say Pat went?
wh-phrase
+ yes-no question (with gap)
Wh-Nominals, used in the same positions as NPs:
Whatever you do () is okay with me.
I don’t know what to do () or how to do it.
“Tough movement” in complements of some adjectives:
Chris is easy for anyone to talk to ().
Why “Long-Distance”?
NP
NP
SBAR
IN
S
NP
VP
S
V
VP
NP
S
V
VP
NP
V
the book
that
Chris
thinks
Pat
said
Kim
read
NP
()
Relation between the Filler and Gap
The wh-phrase can fill an obligatory constituent in the relative clause:
the student who () got the scholarship
the student whom the professor saw ()
the student whom the dean said hello to ()
The wh-phrase can act as an optional adverbial on the relative clause:
the child to whom I read the book
the city where I was born
Ambiguities more likely in latter case:
the man to whom John said he sold the book
?
“Pied Piping”
a man the brother of whom I have met ()
a system whose convenience consumers like ()
The wh-word is identical to the head noun.
The whole wh-phrase fills the gap.
All the Syntax of English (almost)
Structure of the clause
Structure of the noun phrase
Adverbials
Relative clauses and other long-distance
dependencies
Conjunctions (or Coordination)
Coordination
Coordinate conjunctions: and, or, but
Conjunction constructions can be quite complicated, in general:
Pat likes Chris, and Kim too. (ambiguous)
Pat likes and wants to go on a date with Chris.
The teacher likes intelligent and enthusiastic students. (ambiguous)
The three tall English and two short Danish men
John believes Mary likes him and is happy. (ambiguous)
John likes Mary, and Pat Chris.
Sudan is an underdeveloped country, the northern half of which is
desert and the southern jungle.
But .....
Coordination of Like Constituents
The vast majority of coordination constructions conjoin like constituents:
S and S:
John likes Mary, and Chris likes Pat.
VP CC VP: Chris likes Pat but hates Kim.
VB CC VB: Everybody either loves or hates Hillary.
NP and NP: Chris and Pat like Kim.
NN and NN: the man and woman
JJ and JJ: the tall and handsome man
PP and PP: We went over the bridge and through the woods.
IN and IN: Chris ran to and from school
Predicate complements:
Chris is rich, educated, and in the movie industry.
JJ
VBN
PP
Logical Form of Conjunctions
Two cases:
Clause conjunction:
Chris arrived and Pat left.
arrive’(e1,c) & leave’(e2,p) & and’(e3,e1,e2)
logical conjunction
NP conjunction:
Chris and Pat
andn’(e,x,c,p)
set construction
x is the typical element of the set {x,p}
“intelligent and enthusiastic students” is ambiguous:
=> students who are both intelligent and enthusiastic (Clause)
=> intelligent students and enthusiastic students (NP)
Summary of “Shallow” Logical Form
The logical form of a sentence is an existentially quantified conjunction
of propositions:
“The teacher graded the papers slowly.”
==> (E e1,e2,e3,e4,e5,e6,e7,e8,t,p,s)
[the’(e1,t,e2) & teacher’(e2,t) & grade’(e3,t,p) & Past’(e4,e3)
& the’(e5,p,e6) & paper’(e6,p) & Plural’(e6,p,s) & slow’(e7,e3)]
Nouns: book => book’(e,x)
Proper nouns: Chris => Chris’(e,x)
Plural nouns: books => book’(e1,x) & Plural’(e2,x,s)
Prenominal nouns: wine glass => wine’(e1,x) & nn’(e2,x,y) & glass’(e3,y)
Adjectives: tall => tall’(e,x)
Adjectives with complements: able to fly => able’(e1,x,e2) & fly’(e2,x)
Determiners: the => the’(e1,x,e2) = x is uniquely identifiable in context
by means of the property e2
Quantifiers: many => many’(e, s) (a property of the set)
Numbers: three => three’(e,s)
(a property of the set)
Summary of “Shallow” Logical Form
Verbs:
Intransitive: sleep => sleep’(e,x)
Transitive: read => read’(e,x,y)
Ditransitive: give => give’(e,x,y,z)
Infinitive complemenet: want to go => want’(e1,x,e2) & go’(e2,x)
Sentential complement:
say that he left => say’(e1,x,e2) & Past’(e2,e3) & leave’(e3,y)
Prepositions:
P NP: in Tampa => in’(e,x,t)
P S: before he left => before’(e1,x,e2) & Past’(e2,e3) & leave’(e3,y)
(x argument (subject) is the S or NP the PP modifies)
Adverbs:
run quickly => quick’(e1,e2) & run’(e2,x)
Summary of “Shallow” Logical Form
Conjunction:
Clause conjunction:
Chris arrived and Kim left
=> arrive’(e1,c) & leave’(e2,k) & and’(e3,e1,e2)
NP conjunction:
Chris and Pat => andn’(e1,x,c,p)