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DTSTART:20251026T030000
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UID:calendar.29371.field_data.0@oba.diag.uniroma1.it
DTSTAMP:20260408T164733Z
CREATED:20250606T075348Z
DESCRIPTION:Abstract:A classical result by Lovász asserts that two graphs G
  and H are isomorphic if and only if they have the same left profile\, tha
 t is\, for every graph F\, the number of homomorphisms from F to G coincid
 es with the number of homomorphisms from F to H. A similar result is also 
 known to hold for right profiles\, that is\, two graphs G and H are isomor
 phic if and only if for every graph F\, the number of homomorphisms from G
  to F coincides with the number of homomorphisms from H to F. During the p
 ast several years\, there has been a study of equivalence relations that a
 re relaxations of isomorphism obtained by restricting the left profile or 
 the right profile to suitably restricted classes of graphs\, instead of th
 e class of all graphs. Furthermore\, a notion of a query algorithm based o
 n homomorphism counts was recently introduced and investigated. The aim of
  this talk is to present an overview of some of the main results in this a
 rea with emphasis on the connections with finite model theory\, database t
 heory\, and constraint satisfaction.Bio:Phokion Kolaitis is a Distinguishe
 d Professor Emeritus at UC Santa Cruz and a Principal Research Staff Membe
 r at the IBM Almaden Research Center. His research interests include princ
 iples of database systems\, logic in computer science\, and computational 
 complexity. Kolaitis is a Fellow of the American Association for the Advan
 cement of Science (AAAS)\, a Fellow of the Association for Computing Machi
 nery (ACM)\, a Foreign Member of the Finnish Academy of Science and Letter
 s\, a Foreign Member of Academia Europaea.  He is also the recipient of tw
 o IBM Research Division Outstanding Innovation Awards\, an IBM Research Di
 vision Outstanding Technical Achievement Award\, a co-winner of both the 2
 008 and the 2014 ACM PODS Alberto O. Mendelzon Test-of-Time Award\, a co-w
 inner of the 2013 International Conference on Database Theory Test-of-Time
  Award\, and a co-winner of the 2020 Alonzo Church Award for Outstanding C
 ontributions to Logic and Computation.Wikipedia Entry: https://en.wikipedi
 a.org/wiki/Phokion_G._KolaitisPersonal Website: https://users.soe.ucsc.edu
 /~kolaitis/ 
DTSTART;TZID=Europe/Paris:20250623T150000
DTEND;TZID=Europe/Paris:20250623T150000
LAST-MODIFIED:20250606T075556Z
LOCATION:Aula Magna DIAG
SUMMARY:Homomorphism Counts: Expressive Power and Query Algorithms - Prof. 
 Phokion G. Kolaitis
URL;TYPE=URI:http://oba.diag.uniroma1.it/node/29371
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