Download - Symbols and Language Lexical Relations SIMS 202 Profs. Hearst & Larson UC Berkeley SIMS Fall 2000
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Symbols and LanguageLexical Relations
SIMS 202Profs. Hearst & Larson
UC Berkeley SIMSFall 2000
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Today
Symbols and Language Lexical Relations
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What is a symbol?
Something that stands for or suggests something else.
An arbitrary conventional sign used in writing or printing to represent:– Operations, quantities, elements,
relations, qualities– (Merriam-Webster’s Collegiate)
What is meant by sign and represent?
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Recognizing Symbols
What is/are this/these symbol(s)?– Two overlapping squares? – Eight horizontal and eight vertical
lines?
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Symbols and Language
Abstract concepts are difficult to express in a computer.
Combinations of abstract concepts are even more difficult to express:– time– shades of meaning– social and psychological concepts– causal relationships
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Symbols and Language
The Dog.
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Symbols and Language
The Dog.
The dog cavorts.
The dog cavorted.
The picture doesn’t really show the manner or tense.
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Symbols and Language
The man.
The man walks.
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Symbols and Language
The man walks the cavorting dog.
So far, we can sort of show the meaning in pictures.
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Symbols and Language
As the man walks the cavorting dog, thoughtsarrive unbidden of the previous spring, so unlikethis one, in which walking was marching anddogs were baleful sentinels outside unjust halls.
What is the relation between the symbols and the meaning?
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Symbols and Language
Language only hints at meaning. Most meaning of text lies within our
minds and common understanding.– “How much is that doggy in the window?”
» how much: social system of barter and trade (not the size of the dog)
» “doggy” implies childlike, plaintive, probably cannot do the purchasing on their own
» “in the window” implies behind a store window, not really inside a window, requires notion of window shopping
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Correspondences between Symbols and Meaning
Consider made-up languages– Codes used by espionage agents
» “Pope” means a particular piece of microfilm» “Denver” indicates a particular mailbox
People remember the “gist” instead of the actual words used.– This implies the actual words used are not
very salient; what matters is the meaning.
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Semantics: The Meaning of Symbols
Semantics versus Syntax– add(3,4)– 3 + 4(different syntax, same meaning)
Meaning versus Representation– What a person’s name is versus who they
are.» A rose by any other name...
– What the computer program “looks like” versus what it actually does.
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Semantics Semantics: assigning meanings to
symbols and expressions.– Usually involves defining:
»objects»properties of objects» relations between objects
– More detailed versions include »events» time»places»measurements (quantities)
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The Role of Context
The concept associated with the symbol 21 means different things in different contexts.– Examples?
The question “Is there any salt?”– Asked of a waiter at a restaurant.– Asked of an environmental scientist
at work.
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What’s In a Sentence?
“A sentence is not a verbal snapshot or movie of an event. In framing an utterance, you have to abstract away from everything you know, or can picture, about a situation, and present a schematic version which conveys the essentials. In terms of grammatical marking, there is not enough time in the speech situation for any language to allow for the marking of everything which could possibly be significant to the message.”
Dan Slobin, in Language Acquisition: The state of the art, 1982
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Lexical Relations
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Lexical Relations
Conceptual relations link concepts– Goal of Artificial Intelligence
Lexical relations link words– Goal of Linguistics
How do they differ?
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Major Lexical Relations
Synonymy Polysemy Metonymy Hyponymy/Hyperonymy Meronymy Antonymy
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WordNet
A large lexical database Developed over the last ten years Started by George Miller
– A new book out about it (Fellbaum 98)– Some nice interfaces available on the Web
» http://www.cogsci.princeton.edu/~wn/main» http://www-inf.enst.fr/~milc/wordnet.html
– Lexical Freenet – find links between words using Wordnet
» http://www.lexfn.com/
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Synonymy
Different ways of expressing related concepts
Examples– cat, feline, Siamese cat
Overlaps with basic and subordinate levels Synonyms are almost never truly
substitutable:– Used in different contexts– Have different implications
» This is a point of contention.
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Polysemy
Most words have more than one sense– Homonym: same word, different meaning
»bank (river)»bank (financial)
– Polysemy: different senses of same word»That dog has floppy ears./»She has a good ear for jazz.»bank (financial) has several related senses
the building, the institution, the notion of where money is stored
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Metonymy
Use one aspect of something to stand for the whole– The building stands for the institution
of the bank.– Newscast: “The White House released
new figures today.”– Waitperson: “The ham sandwich
spilled his drink.”
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Hyponymy/Hyperonymy
ISA relation Related to Superordinate and
Subordinate level categories– hyponym(robin,bird)– hyponym(bird,animal)– hyponym(emu,bird)
A is a hypernym of B if B is a type of A A is a hyponym of B if A is a type of B
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Meronymy
Parts-of relation– part of(beak, bird)– part of(bark, tree)
Transitive conceptually but not lexically:– The knob is a part of the door.– The door is a part of the house.– ? The knob is a part of the house ?
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Antonymy
Lexical opposites– antonym(large, small)– antonym(big, small)– antonym(big, little)– but not large, little
Many antonymous relations can be reliably detected by looking for statistical correlations in large text collections. (Justeson &Katz 91)
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Thesauri keep track of meanings
Polysemy: same word, different senses of meaning– slightly different concepts expressed
similarly Synonyms: different words, related
senses of meanings– different ways to express similar
concepts Thesauri help draw all these together
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Important Distinction
Lexical Relations vs. Conceptual Relations
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Lexical vs. Conceptual
People associate an adjective with its antonym on a lexical level (K. J. Miller ‘98)
»Example:Opposite of “large” is ___?
The answer is not “little”.
»Standardized tests take advantage of this.
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What is an Ontology?
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Ontology From Merriam-Webster’s Collegiate:
– A branch of metaphysics concerned with the nature and relations of being.
– A particular theory about the nature of being or the kinds of existence.
More prosaically:– A carving up of the world’s meanings.– Determine what things exist, but not how
they inter-relate. Related terms:
– taxonomy, dictionary, category structure
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Building an Ontology
Typical first step:– What are the classes?– What are their attributes?
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Attributes and Values
Classes have attributes– Attribute is the TYPE of information
» (kind of like a data type in a programming language)
– Attributes have VALUES that fit their TYPE»attribute TYPE: integer, VALUE: 9»attribute TYPE: suit, VALUE: club, heart, spade,
diamond»attribute TYPE: name, VALUE: Juanita, Dekai, Laura
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Attributes vs. Classes
How do we make this distinction? Say we are clothing manufacturers.
– Fur is a class– Animal is an attribute
Say we are naturalists.– Animal is a class– Fur is an attribute
This example shows that one user’s classes are another user’s attributes
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Let’s Design a Cookbook
What are the categories and attributes?
How should we organize them for the:– Table of contents– Index
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Next Time
Facets vs. Hierarchies Psychology of Category Structure