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/2007/newsitem/2106/22-
 November-2007-Logic-Tea-Luc-Segoufin
DTSTAMP:20071118T000000
SUMMARY:Logic Tea, Luc Segoufin
ATTENDEE;ROLE=Speaker:Luc Segoufin
DTSTART;TZID=Europe/Amsterdam:20071122T160000
DTEND;TZID=Europe/Amsterdam:20071122T170000
LOCATION:Room P.019, Euclides Building, Plantage M
 uidergracht 24, Amsterdam
DESCRIPTION:In this talk I will consider <-inv-FO,
  order-invariant first-order, over finite structur
 es. <-inv-FO is the class of first-order formulas 
 that use an extra predicate interpreted as a linea
 r order, but such that the truthness of the formul
 a does not depend on the choice of the linear orde
 r. Over arbitrary structures, it is a simple conse
 quence of Craig Interpolation Theorem to show that
  <-inv-FO and FO have the same expressive power. O
 ver finite structures it is possible to show that 
 <-inv-FO express strictly more than FO. I will the
 n show that over simple strucutres, such as words 
 or trees, <-inv-FO=FO. To achieve this I will intr
 oduce and use an algebraic characterization of FO 
 over trees.    The Logic Tea homepage can be found
  at https://www.illc.uva.nl/logic_tea/. For more i
 nformation, please contact Joel Uckelmann (juckelm
 a at science.uva.nl) or Edgar Andrade (E.J.Andrade
 Lotero at uva.nl).
X-ALT-DESC;FMTTYPE=text/html:\n      <p>\n        
 In this talk I will consider &lt;-inv-FO, order-in
 variant first-order, over finite structures. &lt;-
 inv-FO is the class of first-order formulas that u
 se an extra predicate interpreted as a linear orde
 r, but such that the truthness of the formula does
  not depend on the choice of the linear order. Ove
 r arbitrary structures, it is a simple consequence
  of Craig Interpolation Theorem to show that &lt;-
 inv-FO and FO have the same expressive power. Over
  finite structures it is possible to show that &lt
 ;-inv-FO express strictly more than FO.  I will th
 en show that over simple strucutres, such as words
  or trees, &lt;-inv-FO=FO. To achieve this I will 
 introduce and use an algebraic characterization of
  FO over trees.\n      </p>\n    \n      <p>\n    
     The Logic Tea homepage can be found at\n      
   <a target="_blank" href="https://www.illc.uva.nl
 /logic_tea/">https://www.illc.uva.nl/logic_tea/</a
 >.\n        For more information, please contact\n
         Joel Uckelmann (<a class="email">juckelma 
 <span class="at">at</span> science.uva.nl</a>)\n  
       or Edgar Andrade (<a class="email">E.J.Andra
 deLotero <span class="at">at</span> uva.nl</a>).\n
       </p>\n    
URL:/NewsandEvents/Archives/2007/newsitem/2106/22-
 November-2007-Logic-Tea-Luc-Segoufin
END:VEVENT
END:VCALENDAR