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3. Linguistic Essential
인공지능 연구실
강미영
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3. Linguistic Essential
3.1 Parts of Speech and Morphology
–
–
–
–
Nouns and pronouns
Determiners and adjectives
Verbs
Other parts of speech (adverbs, prepositions, particles)
3.2 Phrase Structure
–
–
–
–
Phrase structure grammars
Dependency: Arguments and adjuncts
X' theory
Phrase structure ambiguity
3.3 Semantics and Pragmatics
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3.1 Parts of Speech and Morphology (1-1)
• Parts of speech(POS) : Syntactic or grammatical categories
– show similar syntactic behavior
– Three important parts of speech
• Nouns:
(refer to people, animals, concepts and things)
• Verb:
(used express the action in the sentence)
• Adjectives: (describe properties of nouns)
Children eat sweet candy
– Substitution test: most basic test for words belonging to the same class
The
sad
intelligent
green
fat
…
one is in the corner
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3.1 Parts of Speech and Morphology (1-2)
• Many words have multiple parts of speech
Too much boiling will candy the molasses
Have a candy from the box
• Word classes
1. open (or lexical) categories
• nouns, verbs, adjectives
• large number of members
• new words added
2. closed (or functional) categories
• prepositions (of, on), determiners(the, a)
• a few members
• normally have a clear grammatical use
• Various parts of speech for a word listed in a lexicon
• Systems of parts of speech :
– Tradition: about 8 categories
– Corpus linguists: sets of abbreviations for naming word classes ( POS tags )
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3.1 Parts of Speech and Morphology (2-1)
• Word categories systematically related by Morphological
processes
– Formation of the plural form from the singular form of the noun
• Dog  Dog-s
• Morphology
– Very important in NLP
– Language is productive
새로운 단어
우리가 이미 알고 있는 단어와 관련
새로운 단어의 형태론적 절차를 이해
많은 통사론적 의미론적 속성을 이해 가능
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3.1 Parts of Speech and Morphology (2-2-1)
• Types of Morphological processes
1. Inflexion
• Systematic modifications of a root for by means of prefixes and
suffixes
• indicatite grammatical distinction (singular/ plural)
– Varies features (tense, number, plurality)
• No change word class or meaning significantly
• Inflectional forms of a word = manifestations of a single lexeme
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3.1 Parts of Speech and Morphology (2-2-2)
2. Derivation
• Less systematic (wide  widely/ old  *oldly/ difficult  *difficultly)
• More radical change of syntactic category
• Involves a change in meaning
wide(adj)
derivation
widely(adv)
a wide river : 넓은 영역 퍼져있는
It is widely believed : 넓게 퍼져있는 사람들 사이에
• Suffixes of derivation: -en(weak-en)/ -able(accept-able)/ -er(teach-er)
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3.1 Parts of Speech and Morphology (2-2-3)
3. Compounding: two or more words into a new word
• Noun-noun compounds: combinations of two other nouns
tea kettle, disk driver, college degree
– written as separate words,
– pronounced as a single word,
– Denote a single semantic concept (주로 lexicon에 있음)
• Other compounds involving adjectives, verbs, prepositions
down market, (to)overtake, mad cow disease
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3.1.1 Noun and pronouns (1)
• Entities in the world: people, animals, things
Type of inflection
number
gender
case
– Number
Instances
singular, plural
feminine, masculine, neuter
nominative, genitive, dative, accusative
ex) English (형태론적으로 빈약한 언어)
plural form: + suffix-s
regular
dog :dogs[s]
person:persons[z]
Irregular
child: children
woman:women
speech:speeches[s]
– Gender
English
He, she, it
Latin
-a (fem)
-us (mas)
fili-us (son: male child)
fili-a (daughter: female child)
German
mädchen (daughter: neuter; arbitrary)
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3.1.1 Noun and pronouns (2)
• Cases: nouns appears in different forms when they have different
functions (subject, object, etc.) in the sentence
Latin:
Filius (subject) filium (object)
English : no real case inflections
only case relationship  genitive(describes the possessor)
’s, ’ (after words ending in s)
CLITIC
phrasal affix
- women’s house
- The person you met’s house was broken into
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3.1.1 Noun and pronouns (3)
• Pronoun: variables in that they refer to a person or thing that is
somehow salient in the discourse context
After Mary arrived in the village, she looked for a bed-and-breakfast
– Only words in English which appear in different forms when they are used
as the subject and the object of the sentence
Nominative
Accusative
Subject case
Object case
personal pronouns
– Possessive pronouns: my car, a friend of mine
– Reflexive pronouns: always refer to nearby antecedent in the same
sentence, normally the subject of the sentence
Anaphors : refer to something very nearby in the text
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3.1.1 Noun and pronouns (4)
NN
(singular nouns)
NNP
(proper nouns: ex. Mary, Korea)
NR
(adverbial nouns: ex. west tomorrow)
PPS (3SG)
NNS
(plural nouns)
PPSS (1SG, 2SG, PL)
NNPS
(plurar proper nouns)
NRS
(plural adverbial nouns)
NN$
(possessive singular nouns)
NNS$
(possessive plural nouns)
NNP$
(possessive singular proper nouns)
NNPS$
(possessive plural proper nouns)
NR$
(possessive adverbial nouns)
Nominative
Accusative
PPO
Possessive
PP$ / PP$$ (2nd possessive)
Reflexive
PPL / PPLS (plural)
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3.1.2 Words that accompany nouns (1)
• Determiners(한정사) and adjectives(형용사)
– Determiner: describe the particular reference of a noun
• Article (the; a(an))
• Demonstratives (this, that)
– Adjectives: describe properties of noun
•
•
•
•
Attributive (Adnominal)
Predicative (complement of be)
Agreement: adjective(& article) agree with the noun (case, number, gender)
Comparative/ Superlative (> Positive (rich))
– -er/ -est (richer/ richest)
– periphrastic forms (more intelligent/ most intelligent )
• Quantifiers (수량사)
– Pre-quantifier (all, many)
– Nominal pronoun (one ,something, anything)
• Interrogative pronouns/ determiners: with or instead of nouns
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3.1.2 Words that accompany nouns (2)
JJ
(positives adj)
JJR (comparatives adj)
JJT (superlatives adj)
JJS (semantically superlatives adj : chief)
NUMBERS
CD (cardinals: one, two…)
OD (ordinals: first, second…)
AT
(articles)
DT
(singular determiners: this, that)
DTS
(plural determiners: these, those)
DTI
(단 복수 구분 없음: some, any)
DTX
(double conjunction: either, neither)
WDT (wh-determiner: what, which)
WP$ (possessive wh-pronoun: whose)
ABN (pre-quantifier: all, many)
PN
(nominal pronoun: one, something)
EX
(문두에 쓰인 형식적인 주어: there)
WPO (objective wh-pronoun: whom, which,
that)
WPS (nominative wh-pronoun: who, which,
that)
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3.1.3 Verbs
• Describe action
• Morphological forms of regular verbs
VB
Base form
take
VBD
Past tense
took
VBG
Gerund & present participle
taking
VBN
Past participle
taken
MD
Modal auxiliaries
can, may, must, could, might…
see table 4.6 !
be, have, do…
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3.1.4 Other parts of speech
• Adverbs
– Modify a verb (specify place, time, manner, degree)
– Modify adjectives and adverbs
• Preposition
– Express spatial relationships
• Particle(후치사<접미사: ! suffix>)
– Subclass of prepositions: most prepositions do double duty as particles
– Construct phrasal verb entering into strong bounds with verbs
– Separate lexical entry ( different syntactic semantic properties)
• preposition  particle
She ran up a hill She ran up a bill
• Conjunctions & complementizers
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3.1.4 Other parts of speech
RB
Ordinary adverb
simply, late, well, little
RBR
Comparative adverb
later, better, less
RBT
Superlative adverb
latest, best, least
QL
Qualifier
=degree adverb
very, too, extremely
(형용사나 부사만을 수식)
QLP
Post-qualifier
enough, indeed
WQL
Wh-qualifier
how
WRB
Wh-adverb
how, when, where
IN
Prepositions
RP
Particles
CC
Conjunctions
and, or, but
CS
Subornating conjunctions
( Complementizers: that)
that, because, if, before,…
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3.2 Phrase structure(구구조) (1)
• Syntax: study of the regularities and constraints of word order and
phrase structure
• Constituents(구성요소) 3.2.1 Phrase structure grammars (1)
– able to occur various positions
– uniform syntactic possibilities for expansion
She
The woman
The tall woman
The very tall woman
The tall woman with sad eyes
…
saw
him
the man
the short man
the very short man
the short man with red hair
….
– Paradigmatic relationship: all element that can be replaced for each other in
certain syntactic position are member of one paradigm.
– Syntagmatic relationship: 하나의 구(phrase (syntagma))를 이루는 둘 이상의
단어(구) 사이의 관계
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3.2 Phrase structure(구구조) (2)
• Typical English phrase structure
– Rewrite rule
S
NP
That man
VP
VBD
NP
caught
the butterfly
PP
IN
NP
with
a net
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3.2 Phrase structure(구구조) (3)
• Noun phrases (NP)
– Head: noun
– Arguments of verb
(determiner) + (adjective phrase) + noun + (post-modifier)
(optional)
(head)
prepositional phrases,
clausal modifiers
• Prepositional phrases (PPs)
– Head: preposition
– Contain a noun phrase complement
– Express spatial, temporal locations, etc.
• Verb phrases (VP)
– Head: verb
– Organize all elements of the sentence
• Adjective phrases (APs) : very sure of herself, quite certain to succeed
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3.2.1 Phrase structure grammars (1)
• Word order
– Change in meaning : English
– Do not change in meaning: Latin ( = free word order language)
– Declaratives, Interrogatives (inversion), Imperatives
• Rewrite rules (constituency를 보여줌1) 3.2 Phrase structure (1)
– used to generate sentences
– A  B, A  B + C
S

:
NP VP
AT

AT NNS
NP
VP


AT NN
the
chidren
NNS 
students
NP PP
mountains
VP PP
slept
VBD
VBD NP
VBD

Generation
S
NP VP
 AT NNS VBD
The children slept
ate
saw
etc.
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3.2.1 Phrase structure grammars (2)
• Tree (constituency를 보여줌 2)
– Terminal nodes:분석되는 문장의 실제 어형
– Non terminal nodes (Internal nodes): 통사적 그룹, 구
– The order of daughters generates the word order of sentence
S
NP
VP
AT
NNS
VBD
The
children
slept
• Bracketing (constituency를 보여줌 3): grouping
[S [NP [AT THE] [NNS children]] [VP [VBD ate] [NP [AT the] [NN cake]]]]
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3.2.1 Phrase structure grammars (3)
• Recursivity: recursive expansions
– A property of most formalizations of natural language syntax in terms of rewrite
rules
– The fact that there are constellations in which rewrite rules can be applied an
arbitrary number of times
• Non-local dependencies [challenge some Statistical NLP approach]
– Syntactically dependent even though they occur far apart in a sentence
• Subject-verb agreement(number, person)
• Long-distance dependencies
– Wh-extraction
Should Peter buy a book?
Which book should Peter buy?
– Empty nodes: , e ; ex. NP 
S”
S’
NP
Which book
MD
Should
S
NP
VP
peter VB NP
buy e
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3.2.2 Dependency: Arguments and adjuncts (1)
• Dependency (= dependency grammar 의존문법) : 어떤 문장요소들 간의 의존관
•
계를 바탕으로 문장구조를 표시
문장 성분들 간의 의존관계(종속 관계)를 기술하는 문법:
문장에 들어 있는 상이한 등급의 성분들 중에서 지배 성분에는 어떤 것이 있으며, 또
이 지배 성분에 결합되어 있는 종속 성분에는 어떤 것이 있는가를 기술한 문법
•
의존 관계: 두 문장 성분 사이의 이진 관계(binary relation):
지배 성분(governor head) & 종속 성분(dependent)
– 영어(프랑스어)와 같은 언어:
•어순이 고정되어 있어 구구조(phrase structure)에 기초한 구문분석이 가능
– 어순이 자유로워, 구구조 규칙을 설정하기 어려운 언어 (예: 한국어와 일본어) :
•의존문법에 의한 구문분석 방법 선호
어순이 비교적 자유롭게 나타나는 언어에서 문장의 기본적 구조를 규정하고자 하면 모든 어순,
생략 패턴에 대한 규칙을 설정해야 된다:
I put a pen on the table.
*A pen put I on the table.
*I put a pen.
나는 책상 위에 펜을 놓았다.
펜을 나는 책상 위에 놓았다.
나는 펜을 놓았다.
-영어, 프랑스어, etc.:
제대로 되지 않은 어순 비문
-한국어, etc.:
문법적 (미묘한 의미차이)
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3.2.2 Dependency: Arguments and adjuncts (2)
• Arguments (dependent) of verbs
– express entities that are centrally involved in the activity of the verb
• NPs, PPs, VPs
– Semantic roles
• Agent(동작주)/ Patient(수동자)
– Grammatical relations
• Subject
• Object
– direct object (patient)
– indirect object (recipients(수용자)): prepositional phrase
– Roles(relations) change by voice alternations
• Active & Passive
– English: patient  subject / agent  oblique role (by-phrase)
– Others: change in case marking/ morphology on the verb
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3.2.2 Dependency: Arguments and Adjuncts (3)
• Adjunct (dependent)
–
–
–
–
Less tight link to the verb
Always optional (many complement = obligatory)
Move around more easily than complement
Phrases describing time, place, manner of action, or state
• yesterday, in Paris, with great interest …
– Difficult to distinguish adjunct and compliment
He put the book on the table (obligatory).
He gave his presentation on the stage (optional).
• Intermediate degree of selection ?
He will retire in Florida.
[Statistical NLP: degree of association between a verb and a dependent]
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3.2.2 Dependency: Arguments and adjuncts (4)
• Subcategorization(하위범주화)
– A verb subcategorizes for a particular complement
ex) bring: subcategorizes for an object
– Subcategorized arguments
• Subject,
Predicative adjective,
Participial phrase,
Object,
Bare infinitive,
That-clause,
Prepositional phrase,
Infinitive with to,
Question form clauses
• S’[S Bar] constituent: relative clause, main clause questions
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3.2.2 Dependency: Arguments and adjuncts (5)
• Syntactic regularities about complements:
Subcategorization frame: patterns of arguments
– A particular set of arguments that a verb can appear with
Intransitive verb
NP[subject]
Transitive verb
NP[subject], NP[object]
Ditransitive verb
NP[subject], NP[direct object], NP [indirect object]
Intransitive with PP
NP[subject], PP
Transitive with PP
NP[subject], NP[object], PP
Sentential comp
NP[subject], clause
Transitive with sentential comp
NP[subject], NP[object], clause
• Semantic regularities between constituents
– Selectional restrictions (preferences)
• bark (dogs as subjects)/ eat (edible as objects)
• Violation of selectional preferences: odd sentence
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3.2.3 X’ theory
• Phrases structure rules as presented above do not predict any systematicity in
the way that phrases in natural languages are made, nor any regularities for
the appearance of different kinds of dependents in clauses.
• Head of a phrase: a word
• A broad systematicity in the way dependents arrange themselves around a
head in a phrase: head/complements
NP
N’
Det
The
N
N’
(XP) N”
N’
AP
definitive
(X)
PP
study of subcategorization
Basic 2 level
Can have more or fewer level
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3.2.4 Phrase structure ambiguity (1)
•
rewrite rules used in Parsing
–
•
Parse = phrase structure tree that is constructed from a sentence
Phrase structure ambiguity (syntactic structure ambiguity)
a.
ex) 100 parse for a English sentence
Attachment ambiguity
•
•
Phrase that could have been generated by 2 different nodes
Different attachments have different meanings.
The children ate the cake with a spoon.
Attachment to the verb phrase: (instrument)
Attachment to the noun phrase: (which cake was eaten)
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3.2.4 Phrase structure ambiguity (2)
S
NP
VP
AT
NNS
The
children
VP
VBD
ate
PP
NP
IN
AT NN
the cake
with
NP
AT
a
NN
spoon
S
NP
AT
NNS
The children
VP
VBD
ate
NP
NP
PP
AT NN
IN
the cake
with
NP
AT
a
NN
spoon
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3.2.4 Phrase structure ambiguity (3)
b.
Garden paths(순간적 중의성)
•
Additional words in the sentence that do not seem to belong there
 adopt a spurious parse
 backtrack to try to construct the right parse
•
Rarely problem in spoken language( intonational patterns, pause… )
The horse ran past the barn fell 
The horse fell after it had been raced past the barn
c.
No path at all (not covered by the grammar)
•
Syntactic illformedness (ungrammatical): no interpretation
* Slept chidren the.
•
Semantic abnormality : semantic, pragmatic, cultural oddness
# Coloress green ideas sleep furiously.
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3.3 Semantics and Pragmatics (1)
• Semantics: study of the meaning of words, constructions, and utterances
1. Lexical semantics
– Lexical hierarchy
– Ambiguity: refer to homonymy & polysemy
• Hypernymy: Animal(general) is hypernym of cat(specialized)
• Antonyms: words with opposite meaning; hot / cold , long / short
• Meronymy: part-whole relationship
– Meronym(holonym): tire (car), leaf (tree)
• Synonyms: words with the same or very similar meaning; car / automobile
• Homonyms: different words that are written the same way; bank
• Polyseme: word’s meaning are related; branch
• Homophony: written the same way, identical pronunciation; bass(베이스,
농어)
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3.3 Semantics and Pragmatics (2)
2. Study of how meanings of individual words are combined into the meaning of
sentences (>> discourses)
– Compositionality: the meaning of the whole can be predicted from the meaning
of the parts
• white paper(white), white hair(grey), white skin(rose), white wine(yellow)
– Collocations:
meaning of the whole = sum of the meaning of the part + some additi
onal semantic component that cannot be predicted from the parts
– Idiom: relationship between the meaning of the words and the meaning of the p
hrase is completely opaque
• To kick the bucket ( = die)
– Scope: quantifier have a scope which extends over one or more phrases or clau
ses
• Everyone didn’t go to the movie.
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3.3 Semantics and Pragmatics (3)
– Discourse analysis:
– Relationships between sentences in the text
– Part of pragmatics
– Pragmatics: study of how knowledge about the world and language
conventions interact with literal meaning
– Anaphoric relations: important for information extraction
Mary helped Peter get out of the cab. He thanked her
Mary helped the other passenger out of the cab.
The man had asked her to help him because of his foot injury.
Which Hurricane caused more than a billion dollars worth of d
amage  need pragmatic information
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