Transcript 18-Syntax

Syntax
March 20, 2012
The Last
Quick Write
Flashback
• Way back when, we talked about how it’s possible to
produce infinitely long sentences in a language.
• Example:
John said that Mary thought that Robin knew that Angela
saw that Quinton wanted Sam to think that Becky heard
that Steve wished that Forrest hoped that Bronwen
believed that....
• Idea: our knowledge of language consists of “patterns of
patterns”
Flashback
• We also talked about sentences like the following...
• Colorless green ideas sleep furiously.
• I’m memorizing the score of the sonata I hope to
compose someday.
• ‘Twas brillig, and the slithy toves
Did gyre and gimble in the wabe…
• The claim was that these were “acceptable” sentences of
English, even though they made no sense.
Flashback
• In contrast, the following sentences were not acceptable:
• Green sleep ideas furiously colorless.
• I’m memorizing the perform of the score I sonata to
hope someday.
• Brillig and, slithy and the toves
Wabe gimble in the gyre and did…
• What makes these sentences unacceptable, and the
other sentences acceptable?
Syntax
• Syntax = the rules a language has for putting words
together into sentences
• also: rules for putting words together into phrases
• Important terminology: grammatical
• = strings of words that form possible sentences of a
language
• = conform to the syntactic rules a language has for
putting words together into sentences
• What is grammatical is based on a native speaker’s
judgment of acceptability.
• (descriptive grammar)
On the other hand
• Another important term: ungrammatical
• = string of words that is not a possible sentence in a
language
• = cannot be produced by the syntactic rules of a
language
• What is ungrammatical also reflects a native speaker’s
judgments
• Symbolized with a * before a string of words:
*Green sleep ideas furiously colorless.
Game Plan
• Our goal for today:
• Figure out some basic syntactic rules
• i.e., how languages put words together into larger units
• Let’s start with this observation:
• The rules for putting words together into sentences do not
necessarily yield utterances that make sense.
• Colorless green ideas sleep furiously.
• Q: If syntactic rules are not based on what words mean,
how do they work?
Lexical Categories: Distribution
•
The rules for putting words together into sentences
operate on lexical categories (word types), not word
meanings.
•
Words of each lexical category have a specific syntactic
distribution:
•
•
= the words that may appear around them, in their
“syntactic environment”
Also: there are restrictions on the inflectional affixes
which may attach to them.
•
= “morphosyntax”
Lexical Categories: Distribution
•
Example: Nouns (N)
•
Semantically: refer to persons, places and things
•
Syntactically:
1. May occur after Determiners
•
this book, the water, an idea
•
*this excite, *the somber, *an exactly
2. May be modified with Adjectives
•
•
this funny book, the bad water, a slippery idea
Also, nouns can be plural:
•
the dogs, the cats, *the sombers, *the exactlys
Lexical Categories: Distribution
• Verbs (V)
• Semantically: refer to events and states of affairs
• Syntactically: may appear after Auxiliaries
he can go, she will stay, I have walked
*he can printer, *she will strange, *I have occasionally
• Verbs also take specific inflectional affixes:
• He runs, She plays, It works.
• *He printers, *She stranges, *It precipitouslies.
• He is running, She is playing, It is working.
• *He is printering, *She is stranging, *It is occasionallying
Lexical Categories: Distribution
• Adjectives (Adj)
• Semantically: describe things that nouns refer to
• Syntactically: may be modified by Degree Words
very funny, too wet, quite slippery
*very building, *too walk, *quite these
• Adjectives can also take specific inflectional affixes:
• wetter, funniest
• *buildinger, *walkest
Lexical Categories, part 1
• The familiar lexical categories are “open-class”
categories…
• It is relatively easy to add new items to the category.
• Nouns (N): wickedness, phonology, smock, blog…
• Verbs (V): eat, smash, insult, hug, chillax…
• Adjective (A): creepy, red, humungous, snarky…
• Adverb (Adv): quickly, now, sneakily…
• Note: many adverbs are derived from adjectives.
• But remember that category membership can be fluid...
• Ex: Calvin’s verbing of nouns
Lexical Categories, part 2
• Other lexical categories are “closed-class” or functional
categories…
• It is very difficult to add new items to the category.
• Prepositions (P): to, in, on, near, at, by…
• Pronouns (Pro): I, you, he, she, we, they, it…
• Auxiliaries (Aux): will, can, may, must, should, could…
• Determiner (Det): a, the, this, those, my, their…
• Conjunction (Con): and, but, or…
• Degree (Deg): too, so, very, more, quite…
• The meaning of these categories is harder to define; their
function is to help string words in a sentence together.
Check it out!
• Words
can be categorized on the basis of distributional
and morphosyntactic evidence...
• Even if they don’t mean anything:
'Twas brillig, and the slithy toves
Pro V A Con Det A
N
did gyre and gimble in the wabe.
V V Con V
P Det N
All mimsy were the borogoves,
Det A
V Det
N
And the mome raths outgrabe.
Con Det A N
V
‘Twas Brillig?
• “Brillig” is actually in the
appropriate syntactic frame
for either an adjective or a
noun.
• “It was pleasant…”
• “It was evening…”
• “It was four in the
afternoon….”
A First Hypothesis
• How do we put words together into (grammatical)
sentences?
• A really simple way = string one word category after
another:
S  Det N V Det N
( = “may consist of”)
The child found a puppy.
S  Det A N V P Det N
The slithy toves gimbled in the wabe.
• These syntactic rules could capture patterns of words.
Important Data
•
What’s going on in these sentences?
1. We need more intelligent leaders.
2. I like green eggs and ham.
3. The police shot the terrorists with rifles.
•
 Syntax also puts words together in units that are
smaller than sentences.
•
•
These units are called phrases.
Same string of words, more than one interpretation =
•
more than one phrase structure
•
structural ambiguity
Actual Newspaper Headlines
•
One way in which syntax can enrich your life is through
unintentional humor.
1. HOSPITAL SUED BY SEVEN FOOT DOCTORS
2. LAWYERS GIVE POOR FREE LEGAL ADVICE
3. ENRAGED COW INJURES FARMER WITH AX
4. COMPLAINTS ABOUT NHL REFEREES GROWING UGLY
5. CROWDS RUSH TO SEE POPE TRAMPLE MAN TO DEATH
6. FRENCH OFFER TERRORIST REWARD
Ambiguity (again)
•
There are two ways to represent structural ambiguity in
sentences.
•
Method 1: Bracketing
a. [more intelligent] leaders
b. more [intelligent leaders]
•
Just like morphological bracketing:
•
[[unlock]able]
•
[un[lockable]]
Ambiguity (again)
• Method 2: Phrase Structure Trees
more intelligent leaders
more intelligent leaders
Tree Terminology
node
root node
more intelligent leaders
constituents
more intelligent leaders
Ambiguity (continued)
• Recall: in morphology, each node in a tree had to be a real
word
Adj
Adj
Aff
Verb
Aff
[un-]
[lock]
[-able]
• = not able to be locked
Ambiguity (continued)
• Recall: in morphology, each node in a tree had to be a real
word
Adj
Verb
Aff
Verb
Aff
[un-]
[lock]
[-able]
• = able to be unlocked
Phrases
•
The nodes in a syntactic tree above the word level
represent phrases.
•
•
phrase = string of words that function as a unit
Basic phrase types:
1. Noun Phrases (NP): [intelligent leaders]
2. Verb Phrases (VP): [shoot terrorists]
3. Prepositional Phrases (PP): [with rifles]
4. Adjective Phrases (AP): [more intelligent]
Phrase Phacts
• Every phrase has to have at least one constituent
• This constituent is called the head of the phrase.
• The head determines the phrase’s function, behavior and
category.
• For example, noun phrases have to consist of at least one
noun.
Robin
the book
a picture of Robin
a picture of the unicorn
that weird picture of Bob’s unicorn
In General
• There’s a pattern to how these things work:
• Noun phrases (NPs) are headed by nouns
• NP  N
• Verb phrases (VPs) are headed by verbs
• VP  V
• Prepositional phrases (PPs) are headed by
prepositions
• PP  P
• Adjective phrases (AdjP) are headed by adjectives
• AP  A
• Basic Phrase Structure Rule: XP  X
More About Phrases
•
Beyond the heads, phrases can be expanded with
specifiers and complements.
•
Specifiers precede the head of the phrase;
•
•
they qualify or pick out a particular version of the
head.
Examples:
1. this book
(Determiner specifying noun)
2. very late
(Degree word specifying adjective)
3. often forgets
(Qualifier/Adverb specifying verb)
4. almost in
(Degree word specifying preposition)
Complements
•
Complements always follow the head of the phrase…
•
And provide more information about that head.
1. this book about unicorns
•
PP complement of the head of the NP.
2. very late to class
•
PP complement of the head of the AP.
3. often forgets his hat
•
NP complement of the head of the VP.
4. almost in the basket
•
NP complement of the head of the PP.
X-Bar Theory
• Together, heads and their complements form a phrasal
structure known X’ (“X-bar”).
• Here’s the way phrases (of all kinds) normally break
down:
XP
X’
(Specifier)
• note: heads are the
only obligatory element
in the phrase
• optional stuff is in
parentheses
X
Head
(Complement)