Transcript Constituent Structure - Middle East Technical University

Constituent Structure
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Syntactic Categories
 Parts of speech: Noun, Verb, Adjective, Adverb,
etc.
 Evidence for syntactic categories: child
language.
 The Wug Test (Jean Berko Gleason, 1958) was
designed to understand children’s
understanding of inflection.
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Tongue slips of adult native speakers (Spoonerisms)
“Sir, you’ve hissed my mystery class”.
Intended: “Sir you’ve missed my history class.”
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Ambiguity (Ambiguous sentences)
Lexical ambiguity
 John drove his car to the bank.
 The hunter went home with five bucks in his
pocket.
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Structural ambiguity
This type of ambiguity is caused by grouping
words together in different ways.
 The [tall bishop]’s hat
 (The bishop is tall)
 The tall [bishop’s hat]
 (The hat is tall)
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We can assign different grammatical structures to
the same string of words.
This is evidence showing that words form subgroups (or CONSTITUENTS) within a phrase
or sentence.
These groupings are often crucial in determining
the meaning of a sentence.
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Words belonging to different syntactic categories
Mistrust wounds.
a) “Suspicion hurts people.”
b) “We should mistrust injuries.”
Can you interpret the following sentence?
Time flies.
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Amusing newpaper headlines
Which word causes the ambiguity?
 Reagan Wins On Budget, But More Lies
Ahead
 Squad Helps Dog Bite Victim
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How do we identify a constituent?
 She is crying.
 The little girl wearing a red hat with a blue
ribbon is crying.
(1) Strings of words replacing a single word must
be units (constituents.)
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Malay
 (i) Saya makan
I
eat
ikan besar itu
fish big that
‘I ate/am eating that big fish.’
 (ii)İkan besar itu saya makan
fish
big that I
eat
‘That big fish I ate/am eating.’
(2) When a group of words can be moved as a unit, we can
assume that the group froms a syntactic unit.
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Malay
 Orang
tua
itu
makan ikan besar itu
person
old
that
eat
fish big that
‘That old person ate the big fish.’
 ikan besar itu di-makan oleh anjing saya
fish big that PASS-eat by dog my
‘That big fish was eaten by my dog.’
(3) The same string of words can occur in a variety of positions within the
sentence, e.g. as subject and object.
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Malay
 Orang
tua
itu
makan ikan besar itu
person
old
that
eat
fish big
that
‘That old person ate the big fish.’
 Siapa
makan ikan besar itu
 Who
ate
fish
big
that
‘Who ate that big fish?’
(4) When a group of words are replaced by a question word to
form a content question, we can assume the group of words
forms a unit.
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Siapa makan ikan
besar
Who
ate
fish
big
‘Who ate that big fish?’
Answer1: Orang tua
itu
person
old
Answer2: *tua itu
old
that
itu
that
that
‘that old person
‘old that’
(5) Constituents can form the answer to a content question, whereas a string
of words which is not a syntactic unit is not a possible answer.
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Hierarchy
Each constituent of a larger unit may itself be
composed of smaller constituents.
The CLAUSE is the smallest grammatical unit
which can express a complete proposition.
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A sentence may consist of several clauses.
Can you identify the clauses in the following lines?
Foxes have holes and birds of the air have
nests,
But the Son of Man has no place to lay his
head.
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PHRASE
A single clause may contain several phrases.
The coach’s wife introduced her little
sister to the captain of the football
team.
[to [the captain [of [the [football team]]]]].
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Football team
Of the football team
The captain of the football team
To the captain of the football team
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A single word may contain several morphemes.
Dis-taste-ful
Read-abil-ity
Dis-en-tangle
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This kind of structural organization is called a
PART-WHOLE HIERARCHY: Each unit is
entirely composed of smaller units belonging to
a limited set of types.
This is important in morphology, syntax, and
phonology.
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Identifying syntactic categories
Traditional definitions of parts of speech are based
on semantic properties.
A NOUN is a word than names a person, place, or
thing.
A VERB is a word that names an action or event.
An ADJECTIVE is a word that describes a state.
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 Traditional definitions fail to identify nouns
like happiness, love, destruction, etc.
 They cannot distinguish between the noun love
and the adjective fond of.
 They cannot distinguish the noun fool from the
adjective foolish.
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In Jabberwocky, we were able to distinguish most
parts of speech even though they were mostly
nonsense words.
Also, children are able to form the plurals of
nonsense words or words they’ve never heard
before.
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The identification of syntactic categories cannot be
based on semantic factors.
We need to address the following problems separately:
 Which words belong together in the same
class?
 What name (or label) should we assign to a
given class?
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Answering Question 1
Words that share a number of grammatical
characteristics are assumed to belong to the
same class.
Words that have distinct grammatical
characteristics are assumed to belont to differen
classes.
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Identifying grammatical characteristics
Fool vs foolish
Modification by degree adverb vs
adjective




They are utter fools.
*They are utter foolish.
They are fools.
They are very foolish.
Inflection for number
 Fool, fools
 Foolish, *foolishes
Comparative forms
 Fool-*fooler/*more fool
 Foolish-more foolish
As subject of a clause
 Fools rush in where angels fear
to tread.
 *Fools rush in where angels
fear to tread.
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Answering Question 2
Once the word classes in a particular language have been
identified in this way, they can be assigned a label
(Noun, Verb, etc) based on universal notional patterns.
If there is a class whose prototypical members include
most of the basic terms for concrete objects (dog,
book,house), we would label that class NOUN.
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If there is a class whose prototypical members include
most of the basic terms for volitional actions (run,
dance, eat), we would label that class VERB.
The grammatical criteria used to determine word classes
are diagnostic features rather than definitions.
E.g. In English, not all adjectives can take the comparative and superlative
suffixes.
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Almost all languages have the lexical categories
Noun and Verb, but there is a significant range
of difference among languages.
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PHRASES and PHRASAL CATEGORIES
 A phrase must be a group of words which form
a constituent.
 A phrase is lower in the hierarchy than clauses.
1.
Which phrases belong together in the same class?
2.
What name (or label) should we assign to a given class?
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Answering Question 1
 Internal structure of phrases
e.g. An English noun phrase often begins with a
DETERMINER (a, the, that, this)
 Mutual substitutability: two phrases of the same
category could potentially occur in the same positions.
e.g. Phrases occuring in Object and Subject positions are
NOUN PHRASES.
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Answering Question 2
 In most phrases, there is a core word, called the
HEAD of the phrase.
 We name a phrase by the category of the head.
e.g. That big fish is a NOUN PHRASE because its head is a
noun (fish).
e.g.very beautiful is an ADJECTIVE PHRASE because its head
is an adjective (beautiful).
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How do we know which word in the phrase is the
head?
How do we distnguish the head from the
DEPENDENTS (i.e all the other elements in the
phrase)?
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The head is important because
 it determines the grammatical features of the
phrase as a whole.
 it may determine the number and type of other
elements in the phrase.
 it is more likely to be obligatory than the modifiers
or other non-head elements in the phrase.
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The head determines the grammatical features of the phrase as a whole
The new rice is in the barn.
The new kittens are in the barn.
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The head may determine the number and type of other elements in the phrase.
 Prepositional phrases are complements of the adjective phrase
I am [very grateful to you]
John felt [sorry for his actions.]
angry at someone, proud of someone, worried about something
 Objects are complements of the verb phrase
Mary is [reading a book].
James [showed his photo album to us].
Mary [runs] every morning.
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The head is often obligatory in a phrase.
 [The little girl wearing a red hat with a blue
ribbon] was crying her eyes out.
 [The little girl] was crying her eyes out.
 [The girl] was crying her eyes out.
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The head may be omitted in certain contexts
 The third little girl was smarter than the
second ___.
 The good, the bad, and the ugly
 The rich get richer and the poor get childen.
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 Major categories (can
function as heads of
phrases)
 Noun, verb, adjective,
adverb, preposition
 Minor categories
 Conjunctions,
interjections,
determiners (includes
articles,
demonostratives, and
quantifiers)
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Tree diagrams representing the constituents of a
clause
In analyzing grammatical structure, we need to identify
 The constituent parts which the sentence is formed.
 The order in which these constitutents occur.
The vertical lines inserted between the constitutents are helpful
to describe grammatical structure.
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Tree diagrams
A
B
Mother node
C
Daughter nodes
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 A DOMINATES all of
its daughter nodes; i.e.
The daughters of
daughters, daughters of
its grand-daughters, etc.
 A mother
IMMEDIATELY
DOMINATES its own
daughters.
A CONSTITUENT is a
string of words which is
exhaustively dominated
by some node.
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PP
P
NP
Det
on
the
N
beach
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






N Noun
A Adjective
V Verb
P Preposition
Adv Adverb
Det Determiner
Conj Conjunction





NP Noun Phras
AP ADjective Phrase
VP Verb Phrase
PP Prepositional Phrase
S Sentence or Clause
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 The top-most node in
any tree diagram is
called the ROOT
NODE.
 The terminal nodes at
the bottom are
sometimes called
LEAVES.
 The No Crossing
Constraint: lines from
mother to daughter must
not cross.
 The Single Mother
Constraint: each node
after the root node must
be the daughter of
exactly one other node.
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The motivation for imposing these constraints is
that by allowing crossing lines or multiple
parenthood, we would end up with potentially
complex structures which are never found in
real human languages.
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Phrase Structure Rules
The task of the linguist is to find out the rules
which allow the speakers of a language to
construct and comprehend novel sentences.
The rules needed to produce Phrase Structure
Trees are known as Phrase Structure Rules and
have the following form:
A
B C
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A
B C
 This rule says that a node labelled A may
immediately dominate two daughters labelled B
and C in that order.
 This is a CONTEXT FREE rule, i.e. there is no
conditioning environment stated in this rule.
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Each node of a Phrase Structure tree must be
permitted (or LICENSED) by a phrase structure
rule in order to be legal.
To license (or, to generate) the prepositional
phrase “on the beach” (slide 44), we would
need these rules:
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 PP
 NP
P NP
Det N
 We also need rules to
insert the terminal
elements (lexical
elements), i.e. to hang
leaves on the tree.
 P
{on, in, at,
under, over ...}
 N
{beach, house,
boy, girl, cat ...}
 Det {the, a, an, this,
that, ...}
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The LEXICON (the speaker’s mental dictionary)
 The lexicon includes much
more than a simple list of
words.
 The lexical entry for each
word must include
phonological, semantic,
morphological, and syntactic
information.
 Instead of having lexical
rules like the ones in the
previous slide, we can
simply assume that there is a
general rule of LEXICAL
INSERTION which will
licence a word of any given
category to appear as the
only daughter of a node
which bears the
corresponding category
label.
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Lexical Insertion Rule
Any lexical category (N, V, etc) may have a sinlge
daughter node which is a specific lexical item
of the same category.
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Notational devices to combine two or more Phrase
Structure Rules
 a) A
b) A
c) A
B (C)
B
B C
 a) X
b) X
c) X
Y
Z
Y
Z
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Pronouns and proper names
In traditional grammar, pronouns and proper
names are not considered as “phrases” in the
sense we use them in linguistics.
 I collapsed.
(pronoun)
 John collapsed.
(proper name)
 The old school collapsed. (noun phrase)
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The subject of a clause may be expressed as a pronoun, a
proper name, or a common noun phrase.
S
pronoun
proper name V
noun phrase
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The object of a preposition can be a pronoun, a
proper name, or a common noun phrase.
behind me
behind John
behind the old school house
PP
P
pronoun
proper name
noun phrase
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Notice that the material inside the braces in PS
rules in slides 56 and 57 are exactly the same.
The same set of alternatives may show up in other
PS rules as well, i.e., in almost every position
where a name can occur, we can substitute a
pronoun or a common noun phrase.
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If we had to list all of these alternatives in every
rule that mentions one of these positions, there
would be a large amount of redundancy in the
rules. We would be missing an important
generalization.
In order to avoid this massive redundancy, we will
use the term NP to refer to any unit which can
appear in a name-like position in the phrase
structure.
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Two New Phrase Structure Rules
S
PP
NP V
P
NP
 Traditional grammars
state that a pronoun
“takes the place of a
noun”, but in fact
pronouns replace whole
NPs.
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Pronouns are never modified by adjectives (but
common nouns are)
 The quick red [fox] jumped over the lazy
brown dog.
 *The quick red [she] jumped over the lazy
brown dog.
 She jumped over him.
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Proper nouns are not modified by determiners or
adjectives either.
Some unusal cases exist:
 You are the first Emily
I’ve ever met.
 We will assume that
pronouns and proper
names are lexical items
whose lexical entry
specifies that they
belong to category NP,
rather than N.
 They may appear in tree
diagrams as immediate
daughters of an NP
node.
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 This is the end of the lecture on constituency.
You can now do the exercises in Kroeger, pp.
47-50.
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