BEGIN:VCALENDAR VERSION:2.0 PRODID:ILLC Website X-WR-TIMEZONE:Europe/Amsterdam BEGIN:VTIMEZONE TZID:Europe/Amsterdam X-LIC-LOCATION:Europe/Amsterdam BEGIN:DAYLIGHT TZOFFSETFROM:+0100 TZOFFSETTO:+0200 TZNAME:CEST DTSTART:19700329T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:+0200 TZOFFSETTO:+0100 TZNAME:CET DTSTART:19701025T030000 RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU END:STANDARD END:VTIMEZONE 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
\n Stochastic Tree Substitution Grammars (STSGs), suc h as used in Data-Oriented Parsing, have great lin guistic advantages, essentially merging "cons truction grammar" with "probabilistic li nguistics". However, from a computational lin guistics perspective, they pose a number of comput ational challenges that have not yet been satisfac torily solved.\n
\n\n Two fundamental and related problems are "the pr oblem of estimation" -- estimating the weight s of an STSG from observed subtree frequencies in a tree bank -- and "the problem of expectatio n" -- 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
\n \n\n For more informat ion, see\n http://staff. science.uva.nl/~jzuidema/CLS/\n
URL:/NewsandEvents/Archives/2005/newsitem/1087/23- November-2005-Computational-Linguistics-Seminar-Je lle-Zuidema END:VEVENT END:VCALENDAR