1 Comparable Corpora Within and Across Languages, Word Frequency Lists and the KELLY Project Adam Kilgarriff Lexical Computing Ltd Lexicography MasterClass Universities of Leeds and Sussex

Malta, May 2010Kilgarriff: BUCC 2 Two corpora are comparable iff roughly the same text types, subject matter, proportions

Malta, May 2010Kilgarriff: BUCC 3 Two corpora are comparable iff roughly the same text types, subject matter, proportions  Applicable where Different languages Same language  comparable=similar  Any corpus is entirely similar to itself

Malta, May 2010Kilgarriff: BUCC 4 Comparing Corpora  Input Word freq list for c1 Word freq list for c2  For top 500 words compute sum of (observed-expected) 2 /expected  Chi-square-based Discriminates well  Better than spearman rank, cross-entropy

Malta, May 2010Kilgarriff: BUCC s work  Then Very few corpora Purely theoretical interest  Now Web lots of corpora, created to spec Compare…  first question to ask about a new corpus

Malta, May 2010Kilgarriff: BUCC 6 (Monolingual) Word Lists  Define a syllabus  Which words get used in Learning-to-read books (NS children) ‏ NNS language learner textbooks Dictionaries Language testing  NS: educational psychologists  NNS: proficiency levels

Malta, May 2010Kilgarriff: BUCC 7 Should be corpus-based  Most aren't Corpora are quite new  Easy to do better  People will use them Maybe also Governments

Malta, May 2010Kilgarriff: BUCC 8 How  Take your corpus  Count  Voila

Malta, May 2010Kilgarriff: BUCC 9 Complications  What is a word  Words and lemmas  Grammatical classes  Numbers, names...  Multiwords  Homonymy All are slightly different issues for each lg

Malta, May 2010Kilgarriff: BUCC 10 What is a word; delimiters  Found between spaces Not for Chinese: segmentation  English co-operate, widely-held, farmer's, can't  Norwegian, Swedish Compounding, separable verbs  Arabic, Italian Clitics, al,... ...

Malta, May 2010Kilgarriff: BUCC 11 Words and lemmas  Word form (in text) ‏ invading  Lemma (dictionary headword) ‏  Invade for forms invade invades invaded invading  Lemmatisation Chinese, none; English, simple Middling: Swe Nor It Gr Tough: Rus, Pol, Ara

Malta, May 2010Kilgarriff: BUCC 12 Word Families  Derivational morphology efficient/efficiently access/accessible/accessibility available/availability/unavailable  ‘Word families’ tradition  eg: Coxhead, Academic word list Pedagogy: one item to learn But  Where do families end? Different meanings

Malta, May 2010Kilgarriff: BUCC 13 Grammatical classes  brush (verb) and brush (noun) ‏ Same item or different? (both in same word family)  Required (short) list of word classes POS-tagger  Will make mistakes

Malta, May 2010Kilgarriff: BUCC 14 Marginal cases Numbers  twelve, seventeenth, fifties Closed sets  Days of week, months Countries  Capitals, nationalities, currencies, adjectives, languages regional/dialects, political groups, religions  easter, christmas, islam, republican  policies always needed

Malta, May 2010Kilgarriff: BUCC 15 Multiwords  According to Linguistically a word but  Multiword frequency list: top item of the Can't use freqs (alone) to select multiwords

Malta, May 2010Kilgarriff: BUCC 16 Homonymy  bank (river) and bank (money) ‏  Word sense disambiguation We can't do (with decent accuracy) ‏ We can't give freqs for senses  Lists of words not meanings Sometimes disconcerting

Malta, May 2010Kilgarriff: BUCC 17 Corpora  A fairly arbitrary sample of a lg  To limit arbitrariness of wordlist Make it big and diverse  WACKY corpora From web Can do for any language  ??? Comparable ??? Web language: less formal

Malta, May 2010Kilgarriff: BUCC 18 Comparing corpora  Corpora: new  We are all beginners  Best way to get sense of a corpus Compare with another Keywords of each vs. other  Case studies  Sketch Engine functions

Malta, May 2010Kilgarriff: BUCC 19 Comparing frequency lists Web1T –Present from google –All 1-, 2-, 3-, 4, 5-grams with f>40 in one trillion (10 12) words of English that’s 1,000,000,000,000 Compare with BNC –Take top 50,000 items of each –105 Web1T words not in BNC top50k –50 words with highest Web1T:BNC ratio –50 words with lowest ratio

Malta, May 2010Kilgarriff: BUCC 20 Web-high (155 terms) ‏ 61 web and computing –config browser spyware url www forum 38 porn 22 US English (incl Spanish influence –los)‏ 18 business/products common on web –poker viagra lingerie ringtone dvd casino rental collectible tiffany –NB: BNC is old 4 legal –trademarks pursuant accordance herein

Malta, May 2010Kilgarriff: BUCC 21 Web-low Exclude British English, transcription/tokenisation anomalies –herself stood seemed she looked yesterday sat considerable had council felt perhaps walked round her towards claimed knew obviously remained himself he him

Malta, May 2010Kilgarriff: BUCC 22 Observations Pronouns and past tense verbs –Fiction Masc vs fem Yesterday –Probably daily newspapers Constancy of ratios: –He/him/himself –She/her/herself

Malta, May 2010Kilgarriff: BUCC 23 Corpus Factory Many languages General corpus, 100m+ words  Fast  High quality  Comparable across languages

Malta, May 2010Kilgarriff: BUCC 24 Gather Seed words Wikipedia (Wiki) Corpora  many domains  free  265 languages covered, more to come Extract text from Wiki.  Wikipedia 2 Text Tokenise the text.  Morphology of the language is important  Can use the existing word tokeniser tools.

Malta, May 2010Kilgarriff: BUCC 25 Web Corpus Statistics

Malta, May 2010Kilgarriff: BUCC 26 Evaluation For each of the languages, two corpora available:  Web and Wiki  Dutch: also a carefully­designed lexicographic corpus. Hypothesis: Wiki corpora are ‘informational’  Informational --> typical written  Interactional --> typical spoken

Malta, May 2010Kilgarriff: BUCC 27 Evaluation 1st, 2nd person pronouns  strong indicators of interactional language.  English: I me my mine you your yours we us our For each language Take ten commonest 1 st and 2 nd person pronouns For each  Calculate ratio: web:wiki

Malta, May 2010Kilgarriff: BUCC 28 Results: ratios, web:wiki LanguageAverageMinMax Dutch Hindi Telugu Thai Vietnamese

Malta, May 2010Kilgarriff: BUCC 29 KELLY  EU lifelong learning project  Goal: wordcards Word in one lg on one side, other on other Language learning  9 languages, 36 pairs Arabic Chinese English Greek Italian Norwegian Polish Russian Sweden  Partners in 6 countries

Malta, May 2010Kilgarriff: BUCC 30 Method  Prepare monolingual lists  Translate Each into 8 target languages Professional translation services  Integrate, finalise  Produce cards  Goal for each set 9000 pairs at 6 levels

Malta, May 2010Kilgarriff: BUCC 31 Stages  Sort out corpora, tagging  Automatically generate M1 lists names, numbers, countries... keywords vis-a-vis other corpora  Review, compare, prepare M2 lists  Translate  Use translations: M3 lists  Finalise

Malta, May 2010Kilgarriff: BUCC 32 review - how?  points system 2 points for each of 6 levels 12 points for most freq words  deduct points for words in over- represented areas  add in words from other corpora

Malta, May 2010Kilgarriff: BUCC 33 Translation database  On the web  All translations entered into it  Queries like All Swedish words used as translations more than six times All 1:1:1:1... 'simple cases'

Malta, May 2010Kilgarriff: BUCC 34 Using the translations database  Find words not in M2 lists, that need adding Multiwords English look for Probably, the translation of a high-freq word in several of the 8 other lgs So:  add it to English list Homonyms: could be similar

Malta, May 2010Kilgarriff: BUCC 35 Monolingual master lists (M3) ‏  Based on a WAC corpus  Input from other same-lg corpora  And from translations from 8 lgs Useful words which might not be hi-freq  added words/multiwords must be above a lower freq threshold  Target 9000

Malta, May 2010Kilgarriff: BUCC 36 Numbers  Target: 9000 per list  M2 lists Estimate: needed We add multiwords and other 'back-translations'

Malta, May 2010Kilgarriff: BUCC 37 Current status  M1 lists prepared  Lists checked, compared with other lists Corpus-based and other  M2 lists prepared  Translation underway

Malta, May 2010Kilgarriff: BUCC 38 Big problems  Multiwords (as anticipated) ‏  Homonymy (as anticipated) ‏  orange banana alphabet elbow, Hello Worse than anticipated Lists from spoken corpora, learner corpora, needed Relation between  Competence for communicating  The corpora at our disposal

Malta, May 2010Kilgarriff: BUCC 39 Word lists are useful, but ...are they scientific? A tiny bit, occasionally ...could they be scientific? Yes  article of faith By the end of KELLY, we'll have a clearer idea how

Malta, May 2010Kilgarriff: BUCC 40 And now for something completely different: DANTE  Lexical database for English Detailed Accurate Extensive of English Highly corpus-driven 3 yr project 18 expert lexicographers Led by Sue Atkins  BNC, FrameNet, Euralex, COBUILD...  English side, New English-Irish dictionary  Available for NLP research imminently