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Natural Language Processing. Spring 2007 V. “Juggy” Jagannathan. Course Book. Foundations of Statistical Natural Language Processing. By Christopher Manning & Hinrich Schutze. Chapter 3. Linguistic Essentials January 22, 2007. Parts of Speech and Morphology.

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natural language processing

Natural Language Processing

Spring 2007

V. “Juggy” Jagannathan

chapter 3

Chapter 3

Linguistic Essentials

January 22, 2007

parts of speech and morphology
Parts of Speech and Morphology
  • Syntactic/Grammatical categories – Parts of Speech (POS)
    • Nouns – refer to people, animal, concepts & things
    • Verbs – to express action in a sentence
    • Adjectives – describe properties of nouns
      • Substitution test for adjectives
      • Ex: The {sad, intelligent, green, fat…} one is in the corner.
word class lexical categories
Word class/lexical categories
  • Open or lexical categories
    • Nouns, verbs and adjectives that have a large membership and continually grows as new words are added to the language
  • Closed word or functional categories
    • Prepositions and determiners
      • Ex. Of, on, the, a
  • Words are listed in a “dictionary” referred to by linguists as the “lexicon”
  • Parts of Speech tagging – 8 categories – referred to as POS tags.
  • Corpus Linguists use more fine grained tagging
  • Various corpus have been tagged extensively and the pioneering one is the Brown corpus.
    • Adjectives in Brown corpus are referred by the tag “JJ”
morphological process
Morphological process
  • Source:
    • “Definition A morphological process is a means of changing a stem to adjust its meaning to fit its syntactic and communicational context.”
  • Examples
    • Plural form (dog-s) derived from (dog)
morphological processes
Morphological processes
  • Major forms of morphological processes
    • Inflection
      • Systematic modification of a root (stem) form by means of prefixes and suffixes
      • Inflection does not change the meaning of the word but does change word features such as tense and plurality.
      • All of the inflectional forms of a word are grouped as manifestation of a “lexeme”
    • Derivation
      • Can dramatically change the meaning of the derived word.
      • Ex: Adverb “widely” derived from adjective “wide”
      • Ex: suffix use – weak-en; soft-en; understand-able; accept-able; teach-er; lead-er;
  • Compounding
    • Merging of two or more words into a new word (concept)
    • Ex. Disk drive, tea kettle, college degree, down market, mad cow disease, overtake
nouns and pronouns
Nouns and Pronouns
  • Nouns – refers to people, animals and things
    • Dog, tree, person, hat, speech, idea, philosophy
    • Inflection is a process by which stem of a word can be modified to create new word
    • English the only form of inflection is one indicating whether a noun is singular or plural
    • Ex. Dogs, trees, hats, speeches, persons
    • Irregular inflection examples: women
    • Other languages use inflection to convey “gender – masculine, feminine, neuter” and “case – nominative, genitive, dative, accusative).
gender forms
Gender forms
  • Pronouns
    • Masculine (he), feminine (she), neuter (it)
  • Case relationship in English – the genitive case
    • Ex: the woman’s house; the students’ grievances
  • Possessive pronouns
    • Ex: my car
    • Second possessive form of pronoun: a friend of mine
  • Reflexive pronouns – ex. Herself, myself
    • Ex:
      • Mary saw herself in the mirror.
      • Mary saw her in the mirror.
    • Also referred to as “anaphors” must refer to something nearby in the text.
brown tags
Brown tags

** Examples from:

words that accompany nouns determiners and adjectives
Words that accompany nouns: determiners and adjectives
  • Determiners – describe the particular reference of a noun
    • Articles – refers to someone or something
    • “the” refers to someone or some thing we already know about and is being referenced
      • Ex. “the tree” refers to a known tree.
    • “a” or “an” introduces a new reference to some thing that has not appeared before or its identity cannot be inferred from the context.
determiners and adjectives
Determiners and adjectives
  • Demonstratives
    • “this” or “that”
  • Adjectives
    • Describe properties of nouns
    • ex: a red rose, this long journey, many intelligent children, a very trendy magazine.
    • The above is also referred to as: attributive or adnominal.
    • Predicative form of adjective (appearing in the object place of a sentence)
      • Ex. The rose is red. The journey will be long.
  • Agreement, here refers to congruence in gender, case and number between the determiner, adjective and the noun. Many languages, this can be quite complex.
adjectives and brown tags
Adjectives and Brown tags
  • Positive – the basic form of an adjective [JJ]
    • Ex. Rich, trendy, intelligent
  • Comparative [JJR]
    • Ex. Richer, trendier
  • Superlative [JJT]
    • Ex. Richest, trendiest
  • Semantically superlative adjectives [JJS]
    • Ex. Chief, main and top
  • Numbers – are subclasses of adjectives
    • Cardinals [CD]
      • Ex. One, two, and 6,000,000
    • Ordinals [OD]
      • Ex. First, second, tenth
  • Periphrastic forms - forms made by using auxiliary words
    • Ex. More intelligent, most intelligent
brown tags for determiners quantifiers
Brown tags for determiners, quantifiers
  • Determiners
    • Articles [AT]
    • Singular determiners [DT]
      • This, that
    • Plural determiners [DTS]
      • These, those
    • Determiners that can be both singular or plural [DTI]
      • Some, any
    • Double conjunction determiners [DTX]
      • Either, neither
  • Quantifiers
    • Words that express ideas like “all”, “many”, “some”
    • Pre-quantifier [ABN]
      • All, many
    • Nominal pronoun [PN]
      • One, something, anything, something
  • Interrogative pronouns
    • [WDT] – wh-determiner – what, which
    • [WP$] – possesive wh-pronoun: whose
    • [WPO] – objective wh-pronoun: whom, which, that
    • [WPS] – nominative wh-pronoun: who, which, that
phrase structure1
Phrase Structure
  • Noun phrases [NP]
    • Noun is the head of the noun phrase
  • Prepositional phrases [PP]
    • Headed by preposition and contain a NP complement
  • Verb phrases [VP]
    • Headed by a verb
      • Ex. Getting to school on time was a struggle.
  • Adjective phrases [AP]
    • She is very sure of herself
    • He seemed a man who was quite certain to succeed.
phrase structure grammars
Phrase Structure Grammars
  • Syntactic analysis allows us to infer the meaning – meaning completely different in the following two sentences that use the same words
    • Mary gave Peter a book
    • Peter gave Mary a book
  • Some languages the order of the words does not matter – free word order language
non local and long distance dependencies
Non-local and long-distance dependencies
  • Subject-verb agreement
    • The women who found the wallet were given a reward.
  • Long-distance relationship
    • Which book should Peter buy?
  • These dependencies impact statistical NLP approaches
dependency arguments and adjuncts
Dependency: Arguments and adjuncts
  • Dependency
    • Concept of dependents
    • “Sue watched the man at the next table”
      • Sue and man are dependent on watched.
      • The PP “at the next table” is dependent of man. It modifies man.
      • The two phrases can be viewed as “arguments” of the verb “watched”.
  • Semantic roles
    • Agent of an action is the person or thing doing the action [also viewed as subject]
    • Patient – is the person or thing that is being acted on [also viewed as the object]
active passive voice
Active & Passive voice
  • Example
    • Children eat candy.
    • Candy is eaten by children
sub categorization frame
Sub categorization Frame

The set of arguments that a verb can appear with is referred to as sub categorization frame.

x theory
X’ Theory
  • N’ – “N bar nodes”
garden paths
Garden Paths
  • Parsing the following sentence
    • The horse raced past the barn fell.
    • Garden path parse is the phenomenon by which a parse that is generated from “the horse raced past the barn” will have to be abandoned to accommodate “fell”.
ungrammatical constructs
Ungrammatical constructs
  • Parsing may fail or can get multiple parses due to ungrammatical constructs
    • Slept children the
  • Some sentences may be grammatically correct but meaningless
    • Colorless green ideas sleep furiously.
    • The cat barked.
semantics and pragmatics
Semantics and Pragmatics

Lexical Semantics: study of how meanings of individual words are combined into the meaning of sentences.

Hypernymy vs Hyponymy

animal is a hypernym of cat

cat is a hyponym of animal

Antonym – words with opposite meanings

Meronymy – part belonging to a whole

tire is a meronym of a car

Holonym – whole corresponding to a part

Synonyms – words with similar meanings

Homonyms – words that are spelled the same but have different meanings

bank – river bank; bank – a financial institution

Senses Polyseme – if the different senses (meanings) of the word are related. Example “branch” could mean part of a tree; could mean dependant part of an organization.

Ambiguity – lexical ambiguity refers to both homonymy and polyseme

Homophony – homonyms that are also pronounced the same. “bass” for example could mean a fish or low pitched sound – and is NOT a homophone.

  • Once we have the meaning of individual words, we need to assemble them into the meaning of a whole sentence. This is not easy…
    • White paper, white hair, white skin, white wine
    • Only the paper is white!
    • These are example of collocations
  • Idioms – individual word meaning does not predict the meaning of the whole
    • Kick the bucket
    • Carriage return
scope and discourse analysis
Scope and discourse analysis
  • Scope of quantifiers can be tricky
  • Discourse analysis requires resolution of “anaphoric relations”
  • Ex. Mary helped Peter get out of the cab. He thanked her.
  • Anaphoric relations is correctly mapping he to Peter and her to Mary.
other areas in linguistics
Other areas in linguistics
  • Phonetics – study of physical sounds of language – phenomena like consonants, vowels and intonations.
  • Phonology – structure of sound system in languages
  • Sociolinguistics – interactions of social organization and language
  • Historical linguistics – study of how language changes over time
  • Psycholinguistics – study of how language is perceived
  • Mathematical linguistics – use of mathematical modeling approach to linguistics