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Tricks for Statistical Semantic Knowledge Discovery: A Selectionally Restricted Sample Marti A. Hearst UC Berkeley.

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Presentation on theme: "Tricks for Statistical Semantic Knowledge Discovery: A Selectionally Restricted Sample Marti A. Hearst UC Berkeley."— Presentation transcript:

1 Tricks for Statistical Semantic Knowledge Discovery: A Selectionally Restricted Sample Marti A. Hearst UC Berkeley

2 Acquire Semantic Information Goal:

3 ► Something on Finin

4 Tricks I Like Lots o’ Text Unambiguous Cues Rewrite and Verify

5 Trick: Lots o’ Text ► Idea: words in the same syntactic context are semantically related.  Hindle, ACL’90, “Noun classification from predicate-argument structure.”

6 Trick: Lots o’ Text ► Idea: words in the same syntactic context are semantically related.  Nakov & Hearst, ACL/HLT’08 “Solving Relational Similarity Problems Using the Web as a Corpus”

7 Trick: Lots o’ Text ► Idea: bigger is better than smarter!  Banko & Brill ACL’01: “Scaling to Very, Very Large Corpora for Natural Language Disambiguation”

8 Trick: Lots o’ Text ► Idea: apply web-scale n-grams to every problem imaginable.  Lapata & Keller, HLT/NACCL ‘04: “Web as a Baseline: Evaluating the Performance of Unsupervised Web-Based Models for a Range of NLP Tasks” MT candidate selection Article suggestion Noun compound interpretation Noun compound bracketing Adjective ordering > supervised = supervised

9 Limitation ► Sometimes counts alone are too ambiguous. Solution ► Bootstrap from unambiguous contexts.

10 Trick: Use Unambiguous Context ► … to build statistics for ambiguous contexts.  Hindle & Rooth, ACL ’91“Structural Ambiguity and Lexical Relations” Example: PP attachment I eat spaghetti with sauce. Bootstrap from unambiguous contexts: Spaghetti with sauce is delicious. I eat with a fork.

11 Trick: Use Unambiguous Context ► … to identify semantic relations (lexico- syntactic contexts)  Hearst, COLING ’92, “ Automatic Acquisition of Hyponyms from Large Text Corpora” Example: Hyponym Identification

12 Combine Tricks 1 and 2

13 Trick: Use Unambiguous Contexts + Lot’s O’ Text ► Combine lexico-syntactic patterns with occurrence counts.  Kozareva, Riloff, Hovy, HLT-ACL’08. “Semantic Class learning form the Web with Hyponym Pattern Linkage Graphs”.

14 Trick: Use Unambiguous Contexts + Lot’s O’ Text ► Combine (usually) unambiguous surface patterns with occurrence counts.  Nakov & Hearst, HLT/EMNLP’05 “Using the Web as an Implicit Training Set: Application to Structural Ambiguity Resolution”. Left dash cell-cycle analysis  left Possessive marker brain’s stem cell  right Parentheses growth factor (beta)  left Punctuation heath care, provider  left Abbreviation tum. necr.(TN) factor  right Concatenation heathcare reform  left

15 Trick: Use Unambiguous Contexts + Lot’s O’ Text ► Identify a “protagonist” in each text to learn narrative structure  Chambers & Jurafsky, ACL’08 “Unsupervised Learning of Narrative Event Chains”.

16 Trick 3: Rewrite & Verify

17 Trick: Rewrite & Verify ► Check if alternatives exist in text  Nakov & Hearst, HLT/EMNLP’05 “Using the Web as an Implicit Training Set: Application to Structural Ambiguity Resolution”.  Example: NP bracketing  Prepositional ► stem cells in the brain  right ► stem cells from the brain  right ► cells from the brain stem  left  Verbal ► virus causing human immunodeficiency  left ► pain associated with arthritis migraine  left  Copula ► office building that is a skyscraper  right

18 Trick: Use Lexical Hierarchies ► To improve generation of pseudo-words for WSD  Nakov & Hearst, HLT/NAACL’03, “Category-based Pseudo-Words” ► To classify nouns in noun compounds and thus determine the semantic relations between them  Rosario, Hearst, & Fillmore, ACL’02, “Descent of Hierarchy and Selection in Relational Semantics” ► To generate new (faceted) category systems  Stoica, Hearst, & Richardson, NAACL/HLT’07. “Automating Creation of Hierarchical Faceted Metadata Structures”

19 Example: Recipes (3500 docs)

20 Castanet Output (shown in Flamenco)

21 Castanet Output

22

23 Towards New Approaches to Semantic Analysis

24 Ideas ► Inducing Semantic Grammars  Boggess, Agarwal, & Davis, AAAI’91, “Disambiguation of Prepositional Phrases in Automatically Labelled Technical Text”

25 Ideas ► Use Cognitive Linguistics  Hearst, ’90,’92, “Direction-Based Text Interpretation”.  Talmy’s Force Dynamics + Reddy’s Conduit Metaphor  Path Model  Solves: Was the person in favor of or opposed to the idea:

26 Using Cognitive Linguistics ► Talmy’s Theory of Force Dynamics  Talmy, “Force Dynamics in Language and Thought,” in  Talmy, “Force Dynamics in Language and Thought,” in Parasession on Causatives and Agentivity, Chicago Linguistic Society  Describes how the interaction of agents with respect to force is lexically and grammatically expressed.  Posits two opposing entities: Agonist and Antagonist.  Each entity expresses an intrinsic force: towards rest or motion.  The balance of the strengths of the entities determines the outcome of the event. ► Grammatical expression includes using a claused headed by “despite” to express a weaker antagonist.

27 Using Cognitive Linguistics ► Reddy’s Conduit Metaphor  Reddy, “The Conduit Metaphor – A Case of Frame Conflict in Our Language about Language,” in  Reddy, “The Conduit Metaphor – A Case of Frame Conflict in Our Language about Language,” in Metaphor and Thought, Ortony (Ed), Cambridge University Press,  A thought is schematized as an object which is placed by the speaker into a container that is sent along a conduit.  The receiver at the other end is the listener, who removes the objectified thought from the container and thus possesses it.  Inferences that apply to conduits can be applied to communication. ► “Your meaning did not come through.” ► “I can’t put this thought into words.” ► “She is sending you some kind of message with that remark.”

28 Using Cognitive Linguistics ► Combine into the Path Model  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in Text- based Intelligent Systems, Jacobs (Ed), Lawrence Erlbaum Associates,  If an agent favors an entity or event, that agent can be said to desire the existence or “well-being” of that entity, and vice-versa.  Thus if an agent favors an entity’s triumph in a force-dynamic interaction, then the agent favors that entity or event.  But: force dynamics does not have the expressive power for a sequence.   Instead of focusing on the relative strength of two interacting entities, the model should represent what happens to a single entity through the course of its encounters with other entities.   Thus the entity can be schematized as if it were moving along a path toward some destination or goal.

29 Using Cognitive Linguistics ► The Path Model  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in Text- based Intelligent Systems, Jacobs (Ed), Lawrence Erlbaum Associates, 1992.

30 Using Cognitive Linguistics ► The Path Model  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in Text- based Intelligent Systems, Jacobs (Ed), Lawrence Erlbaum Associates, 1992.

31 Using Cognitive Linguistics ► The Path Model  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in  Hearst, “Direction-based Text Interpretation as an Information Access Refinement,” in Text- based Intelligent Systems, Jacobs (Ed), Lawrence Erlbaum Associates, 1992.


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