Combining KR and search: Crossword puzzles

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Combining KR and search Crossword puzzles

• Next Logic representations
• Reading C. 7.4-7.8

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Changes in Homework

• Mar 4th Hand in written design, planned code for
  all modules
• Mar 9th midterm
• Mar 25th Fully running system due
• Mar 30th Tournament begins

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Changes in Homework

• Dictionary
• Use dictionary provided do not use your own
• Start with 300 words only
• Switch to larger set by time of tournament
• Representation of dictionary is important to
  reducing search time
• Using knowledge to generate word candidates could
  also help

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Midterm Survey

• Start after 9AM Friday and finish by Thursday,
  Mar. 4th
• Your answers are important they will affect
  remaining class structure

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Crossword Puzzle Solver

• Proverb Michael Litman, Duke Univ
• Developed by his AI class
• Combines knowledge from multiple sources to solve
  clues (clue/target)
• Uses constraint propogation in combination with
  probabilities to select best target

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Algorithm Overview

• Independent programs specialize in different
  types of clues knowledge experts
• Information retrieval, database search, machine
  learning
• Each expert module generates a candidate list
  (with probabilities)
• Centralized solver
• Merges the candidates lists for each clue
• Places candidates on the puzzle grid

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Performance

• Averages 95.3 words correct and 98.1 letters
  correct
• Under 15 minutes/puzzle
• Tested on a sample of 370 NYT puzzles
• Misses roughly 3 words or 4 letters on a daily
  15X15 puzzle

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Questions

• Is this approach any more intelligent than the
  chess playing programs?
• Does the use of knowledge correspond to
  intelligence?
• Do any of the techniques for generating words
  apply to Scrabble?

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To begin research style

• Study of existing puzzles
• How hard?
• What are the clues like?
• What sources of knowledge might be helpful?
• Crossword Puzzle database (CWDB)
• 350,000 clue-target pairs
• gt250,000 unique pairs
• of puzzles seen over 14 years at rate of one
  puzzle/day

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How novel are crossword puzzles?

• Given complete database and a new puzzle, expect
  to have seen
• 91 of targets
• 50 of clues
• 34 of clue target pairs
• 96 of individual words in clues

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Categories of clues

• Fill in the blank
• 28D Nothing ____ less
• Trailing question mark
• 4D The end of Plato?
• Abbreviations
• 55D Key abbr maj

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Expert Categories

• Synonyms
• 40D Meadowsweet spiraea
• Kind-of
• 27D Kind of coal or coat pea
• pea coal and pea coat standard phrases
• Movies
• 50D Princess in Woolfs Orlando sasha
• Geography
• 59A North Sea port aberdeen
• Music
• 2D Hold Me country Grammay winner, 1988 oslin
• Literature
• 53A Playwright/novelist Capek karel
• Information retrieval
• 6D Mountain known locally as Chomolungma everest

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Candidate generator

• Farrow of Peyton Place mia
• Movie module returns
• 0.909091 mia
• 0.010101 tom
• 0.010101 kip
• 0.010101 ben
• 0.010101 peg
• 0.010101 ray

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Ablation tests

• Removed each module one at a time, rerunning all
  training puzzles
• No single module changed overall percent correct
  by more than 1
• Removing all modules that relied on CWDB
• 94.8 to 27.1 correct
• Using only the modules that relied exclusively on
  CWDB
• 87.6 correct

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Word list modules

• WordList, WordListBig
• Ignore their clues and return all words of
  correct length
• WordList
• 655,000 terms
• WordListBig
• WordList plus constructed terms
• First and last names, adjacent words from clues
• 2.1 million terms, all weighted equally
• 5D 10,000 words, perhaps novelette
• Wordlist-CWDB
• 58,000 unique targets
• Returns all targets of appropriate length
• Weights with estimates of their prior
  probabilities as targets of arbitrary clues
• Examine frequency in crossword puzzles and
  normalize to account for bias caused by letters
  intersecting across and down terms

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CWDB-specific modules

• Exact Match
• Returns all targets of the correct length
  associated with the clue
• Example error it returns eeyore for 19A Pal of
  Pooh tigger
• Transformations
• Learns transformations to clue-target pairs
• Single-word substitution, remove one phrase from
  beginning or end and add another, depluralizing a
  word in clue, pluralize word in target
• Nice X lt-gt X in France
• X for short lt-gt X abbr.
• X start lt-gt Prefix with X
• X city lt-gt X capital
• 51D Bugs chaser elmer, solved by Bugs pursuer
  elmer and the transformation rule X pursuer lt-gt X
  chaser
• http//www.oneacross.com

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Information retrieval modules

• Encyclopedia
• For each query term, compute distribution of
  terms close to query
• Counted 10-k times every times it apears at a
  distance of klt10 from query term
• Extremely common terms (as, and) are ignored
• Partial match
• For a clue c, find all clues in CWDB that share
  words
• For each such clue, give its target a weight
• LSI-Ency, LSI-CWDB
• Latent semantic indexing (LSI) identifies
  correlations between words synonyms
• Return closest word for each word in the clue

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Database Modules

• Movie
• www.imdb.com
• Looks for patterns in the clue and formulates
  query to database
• Quoted titles 56D The Thief of Baghdad role
  abu
• Boolean operations Cary or Lee grant
• Music, literary, geography
• Simple pattern matching of clue (keywords city,
  author, band, etc) to formulate query
• 15A Foundation of Trilogy author asimov
• Geography database Getty Information Institute

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Synonyms

• WordNet
• Look for root forms of words in the clue
• Then find variety of related words
• 49D Chop-chop apace
• Synonyms of synonyms
• Forms of related words converted to forms of clue
  word (number, tense)
• 18A Stymied thwarted
• Is this relevant to Scrabble?

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Syntactic Modules

• Fill-in-the-blanks
• gt5 clues
• Search databases (music, geography, literary and
  quotes) to find clue patterns
• 36A Yerbys A Rose for _ _ _ Maria ana
• Pattern for _ _ _ Maria
• Allow any 3 characters to fill the blanks
• Kindof
• Pattern matching over short phrases
• 50 clues of this type
• type of (A type of jacket nehru)
• starter for (Starter for saxon anglo)
• suffix with (Suffix with switch or sock eroo

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Implicit Distribution Modules

• Some targets not included in any database, but
  more probable than random
• Schaeffer vs. srhffeeca
• Bigram module
• Generates all possible letter sequences of the
  given length by returning a letter bigram
  distribution over all possible strings, learned
  from CWDB
• Lowest probability clue-target, but higher
  probability than random sequence of letters
• Honolulu wear hawaiianmuumuu
• How could this be used for Scrabble?

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Questions

• Is this approach any more intelligent than the
  chess playing programs?
• Does the use of knowledge correspond to
  intelligence?
• Do any of the techniques for generating words
  apply to Scrabble?