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  • Slide 1
  • Type-enabled Keyword Searches with Uncertain Schema Soumen Chakrabarti IIT Bombay www.cse.iitb.ac.in/~soumen
  • Slide 2
  • ICML 2005Chakrabarti2 Evolution of Web search The first decade of Web search Crawling and indexing at massive scale Macroscopic whole-page connectivity analysis Very limited expression of information need Exploiting entities and relationsclear trend Maintaining large type systems and ontologies Discovering mentions of entities and relations Deduplicating and canonicalizing mentions Forming uncertain, probabilistic E-R graphs Enhancing keyword or schema-aware queries
  • Slide 3
  • ICML 2005Chakrabarti3 Disambiguation Named entity tagging Relation tagging Raw corpus Annotated corpus Text index Annotation index Indexer Past query workload stats Ranking engine Question Answer type predictor Keyword match predictor Response snippets WordNet Wikipedia FrameNet KnowItAll Uniform lexical network provider 1 2 3 4
  • Slide 4
  • ICML 2005Chakrabarti4 Populating entity and relation tables Hearst patterns (Hearst 1992) T such as x, x and other T, x is a T DIPRE (Brin 1998) Snowball (Agichtein+ 2000) [left] entity1 [middle] entity2 [right] PMI-IR (Turney 2001) Recognize synonyms using Web stats KnowItAll (Etzioni+ 2004) C-PANKOW (Cimiano+ 2005) Is-a relations from Hearst patterns, lists, PMI
  • Slide 5
  • ICML 2005Chakrabarti5 DIPRE and Snowball Seed tuples Tag mentions in free text Generate extraction patterns Locate new tuples Augmented table the Irving-based Exxon Corporation locationorganization mr Encoded as bag-of-words
  • Slide 6
  • ICML 2005Chakrabarti6 Scoring patterns and tuples Pattern confidence = m + /(m + + m ) over validation tuples Soft-or tuple confidence = Recent improvements: Urn model (Etzioni+ 2005) Uses 5-part encoding DIPRESnowball
  • Slide 7
  • ICML 2005Chakrabarti7 KnowItAll and C-PANKOW A propose-validate approach Using existing patterns, generate queries For each web page w returned Extract potential fact e and assign confidence score Add fact to database if it has high enough score Patterns use chunk info
  • Slide 8
  • ICML 2005Chakrabarti8 Exploiting answer types with PMI From two word queries to two text boxes author; Harry Potter person; Eiffel Tower director; Swades movie city; India Pakistan cricket Keywords search engine snippets Every token/chunk in a snippet is a candidate Elimination hacks that we wont discuss Fire Hearst pattern queries between desired answer type and candidate token/chunk Keywords to match Answer type
  • Slide 9
  • ICML 2005Chakrabarti9 Information carnivores at work Garth Brooks is a country [singer], gift such as wall [clock] person like Paris [Hilton], researchers like Michael Jordan (which one?) KO :: India Pakistan Cricket Series KO :: India Pakistan Cricket Series A web site by Khalid Omar, sort of live from Karachi, Pakistan. cities such as [probe] [probe] and other cities, [probe] is a city, etc.
  • Slide 10
  • ICML 2005Chakrabarti10 Sample output author; Harry Potter J K Rowling, Ron person; Eiffel Tower Gustave, (Eiffel), Paris director; Swades movie Ashutosh Gowariker, Ashutosh Gowarikar What can search engines do to help? Cluster mentions and assign IDs Allow queries for IDs expensive! Harry Potter context in Ron is an author Ambiguity and extremely skewed Web popularity
  • Slide 11
  • ICML 2005Chakrabarti11 Disambiguation Named entity tagging Relation tagging Raw corpus Annotated corpus Text index Annotation index Indexer Past query workload stats Ranking engine Question Answer type predictor Keyword match predictor Response snippets WordNet Wikipedia FrameNet KnowItAll Uniform lexical network provider 1 2 3 4
  • Slide 12
  • ICML 2005Chakrabarti12 Answer type (atype) prediction Standard sub-problem in question answering Increasingly important (but more difficult) for grammar-free Web queries (Broder 2002) Current approaches Pattern matching, e.g. head of noun phrase adjacent to what or which; map when, who, where, directly to classes time, person, place Coupled perceptrons (Li and Roth, 2002) Linear SVM on bag-of-2grams (Hacioglu 2002) SVM with tree kernel on parse (Zhang and Lee, 2004): slim gains Surely a parse tree holds more usable info
  • Slide 13
  • ICML 2005Chakrabarti13 Informer span A short, contiguous span of question tokens reveals the anticipated answer type (atype) Except in multi-function questions, one informer span is dominant and sufficient What is the weight of a rhino? How much does a rhino weigh? How much does a rhino cost? Who is the CEO of IBM? Question parse informer span tagger Learn atype label from informer + question
  • Slide 14
  • ICML 2005Chakrabarti14 Example Pre-in-post Markov process produces question Train a CRF with features derived from parse tree POS, attachments to neighboring chunks, multiple levels First noun chunk? Adjacent to second verb? WhatisthecapitalcityofJapan WPVBZDTNN INNNP NP PP NP VP SQ SBARQ WHNP 0 1 2 3 4 5 6 Level 123 What, is, the capital, city of, Japan (start)
  • Slide 15
  • ICML 2005Chakrabarti15 Atype guessing accuracy Question Trained CRF Filter Informer feature generator Ordinary feature generator Merge Linear SVM Feature vector Atype
  • Slide 16
  • ICML 2005Chakrabarti16 Disambiguation Named entity tagging Relation tagging Raw corpus Annotated corpus Text index Annotation index Indexer Past query workload stats Ranking engine Question Answer type predictor Keyword match predictor Response snippets WordNet Wikipedia FrameNet KnowItAll Uniform lexical network provider 1 2 3 4
  • Slide 17
  • ICML 2005Chakrabarti17 Scoring function for typed search Instance of atype near keyword matches IR systems: hard proximity predicates Search engines: unknown reward for proximity XML+IR, XRank: hard word containment in subtree television was invented in 1925. Inventor John Baird was born person#n#1 IS-A Candidate Selectors Not closest Question: Who invented the television? Atype: person#n#1 Selectors: invent*, television Up to some maximum window
  • Slide 18
  • ICML 2005Chakrabarti18 Learning a scoring function Assume parametric form for a ranking classifier Form of IDF, window size, Can also choose among decay function forms Question-answer pairs give partial orders (Joachims 2004) Recall in top-50, mean reciprocal rank
  • Slide 19
  • ICML 2005Chakrabarti19 Indexing issues Standard IR posting: word {(doc,offsets)} word1 near word2 is standard instance-of(atype) near {word1, word2,} WordNet has 80000 atype nodes, 17000 internal, depth > 10 horse also indexed as mammal, animal, sports equipment, chess piece, Original corpus 4GB, gzipped corpus 1.3GB, IR index 0.9GB, full atype index 4.3GB XML structure indices not designed for fine- grain, word-as-element-node use

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