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Non-Monotonic Reasoning for Parsing Ambiguity

This project aims to address parsing ambiguity using non-monotonic reasoning to explore various types of lexical, structural, and referential ambiguities. The research focuses on automating the selection of lexical entries and enhancing understanding of complex sentence semantics.

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Non-Monotonic Reasoning for Parsing Ambiguity

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  1. Non Monotonic Reasoningfor Disambiguation and Parsing Arthi Murugesan

  2. Outline • what you're doing overall • tell us your plan • what you've accomplished so for • tell us your next few steps • remind us of where you're going to get to in the end

  3. Objective : To deal with ambiguity in Parsing using non-monotonic reasoning • What does parsing & ambiguity share with non-monotonic reasoning ? • All conditions are not predefined • Assume a default but can take it back • ‘bug’ – insect , verb

  4. Defining the problem • Ambiguity : • Distorts a one to one relationship between a sentence and a “meaning” • Types of ambiguity : • Lexical • Structural • Referential …

  5. Lexical ambiguity HPSG Parser – Head-driven Phrase Structure Grammar • Lexical Entry : (Noun Version) • Senses within POS : animal, code error, listening device

  6. Structural Ambiguity I saw an (astronomer) (with a telescope) I (saw) a mouse in the field (with a telescope) Ambiguity in attachment of phrases.

  7. Other Ambiguities • Referential Ambiguity • Grounding in real world (Metonym) • Pronouns • Colloquial way of speech • With stutters • Changing sentences midway

  8. What has been done : det The frog ate the bug. NP The-frog-ate-the-bug VP S Ate-the-bug ate The-frog-NP The-bug-NP The frog the bug

  9. Existing Work • HPSG Parsing mechanism has been used for predetermined unambiguous lexical entries. • Phrases or Output: assertions in the assumption base

  10. Future Step : • To automate the selection of LEXICAL entry: • Probability ( POS tagger ) • Context & Semantics Constraints • Forms Valid sentences? • Maybe earlier heuristics? • Worst case - Alternate worlds • Likely concept

  11. Requirements : • Part of speech: • Probability ( POS tagger) • Integration with a tool [ Penn tree bank or wordnet] • Net Input – Prioritized list of lexical entries of a word • If no sentence is formed : • A mechanism of taking back inferences • A mechanism of introducing the lexical entry on the next greater priority - HARD

  12. Requirements : • Context and Semantics : Semantics of a sentence can be checked against existing knowledge • Semantics of a parsed sentence should be generated (HUGE! Planning to underplay) • Lambda expressions • System's knowledge should in a format interoperable with parser’s output knowledge.

  13. Plan • Shallow implementation : • Prioritized lists • Semantic generation from parse tree • Concentrate on • Varying strengths of rules • Understanding the process by which a proposition or rule is taken back • Explicitly creating worlds & controlling transfer of information between worlds

  14. Expected Output Againand Theory of Working Example word : “bug” Preference of Word senses according to WordNet : (http://wordnet.princeton.edu/perl/webwn) Noun • S: (n) bug (general term for any insect or similar creeping or crawling invertebrate) • S: (n) bug, glitch (a fault or defect in a system or machine) • S: (n) bug (a small hidden microphone; for listening secretly) Verb • S: (v) tease, badger, pester, bug, beleaguer (annoy persistently) "The children teased the boy because of his stammer" • S: (v) wiretap, tap, intercept, bug (tap a telephone or telegraph wire to get information) "The FBI was tapping the phone line of the suspected spy"; "Is this hotel room bugged?" • I saw a bug crawling on the carpet (or) The frog ate the bug - • Using the first sense (Insect) : No contradiction • I bug my dad for money – • Using the first 3 senses (NOUN) will result in no valid sentence. So these lexical senses are to be retracted • The first verb sense forms a valid sentence ( tease, badger, pester or annoy) • The spy used the bug to eavesdrop. • The first sense (Insect) is used • Forms a contradiction in meaning or “Semantics” [ insect cannot eavesdrop ] • (Probably hack this contradiction for now) • Next sense is introduced (defect) and retracted similarly (Another contradiction in semantics) • Finally the third sense (microphone) is introduced and retained

  15. Existing work • http://citeseer.ist.psu.edu/anthony00reasoning.html • Reasoning with Output from Parsing Using World Knowledge (2000)

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