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BEGIN:VEVENT
UID:/NewsandEvents/Archives/2005/newsitem/1087/23-
 November-2005-Computational-Linguistics-Seminar-Je
 lle-Zuidema
DTSTAMP:20051121T000000
SUMMARY:Computational Linguistics Seminar, Jelle Z
 uidema
ATTENDEE;ROLE=Speaker:Jelle Zuidema
DTSTART;TZID=Europe/Amsterdam:20051123T160000
DTEND;TZID=Europe/Amsterdam:20051123T000000
LOCATION:Room P.327, Euclides building, Plantage M
 uidergracht 24, Amsterdam
DESCRIPTION:Stochastic Tree Substitution Grammars 
 (STSGs), such as used in Data-Oriented Parsing, ha
 ve great linguistic advantages, essentially mergin
 g "construction grammar" with "probabilistic lingu
 istics". However, from a computational linguistics
  perspective, they pose a number of computational 
 challenges that have not yet been satisfactorily s
 olved.    Two fundamental and related problems are
  "the problem of estimation" -- estimating the wei
 ghts of an STSG from observed subtree frequencies 
 in a tree bank -- and "the problem of expectation"
  -- calculating the expected subtree frequencies w
 hen generating trees using an STSG with known weig
 hts. A linguistic desideratum for estimation is th
 at it converges to the maximally general STSG out 
 of the possibly many correct ones. I will briefly 
 discuss why none of the existing estimation method
 s fulfills this desideratum. I will then present m
 y recent work on the problem of expectation and di
 scuss how its solution directly suggests an altern
 ative approach to the first problem.    For more i
 nformation, see http://staff.science.uva.nl/~jzuid
 ema/CLS/
X-ALT-DESC;FMTTYPE=text/html:\n      <p>\n        
 Stochastic Tree Substitution Grammars (STSGs), suc
 h as used in Data-Oriented Parsing, have great lin
 guistic advantages, essentially merging &quot;cons
 truction grammar&quot; with &quot;probabilistic li
 nguistics&quot;. However, from a computational lin
 guistics perspective, they pose a number of comput
 ational challenges that have not yet been satisfac
 torily solved.\n      </p>\n      <p>\n        Two
  fundamental and related problems are &quot;the pr
 oblem of estimation&quot; -- estimating the weight
 s of an STSG from observed subtree frequencies in 
 a tree bank -- and &quot;the problem of expectatio
 n&quot; -- calculating the expected subtree freque
 ncies when generating trees using an STSG with kno
 wn weights. A linguistic desideratum for estimatio
 n is that it converges to the maximally general ST
 SG out of the possibly many correct ones. I will b
 riefly discuss why none of the existing estimation
  methods fulfills this desideratum.  I will then p
 resent my recent work on the problem of expectatio
 n and discuss how its solution directly suggests a
 n alternative approach to the first problem.\n    
   </p>\n    \n      <p>\n        For more informat
 ion, see\n        <a target="_blank" href="http://
 staff.science.uva.nl/~jzuidema/CLS/">http://staff.
 science.uva.nl/~jzuidema/CLS/</a>\n      </p>\n   
  
URL:/NewsandEvents/Archives/2005/newsitem/1087/23-
 November-2005-Computational-Linguistics-Seminar-Je
 lle-Zuidema
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