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X-WR-CALNAME:[RATIO] Anantha Padmanabha
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DTSTART:20221030T030000
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RDATE:20231029T030000
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DESCRIPTION:https://ratio.labri.fr/#meetings\nTitle: Algorithms for consist
 ent query answering under primary key constraints\n\nAbstract: Databases o
 ften have constraints. One of the basic constraints is the « primary key c
 onstraint » which states there can be at most one tuple for every primary 
 key. However\, these days it is common to have databases that violate such
  constraints which is called an « inconsistent database ». In particular\,
  if a database violates primary key constraint\, it will contain more than
  one tuple for the same primary key. In this setting\, the notion of a rep
 air is defined by picking exactly one tuple for each primary key (maximal 
 consistent subset of the database). A Boolean conjunctive query q\, is cer
 tain for an inconsistent database D if q evaluates to true over all repair
 s of D. In this context\, we have a dichotomy conjecture that states that 
 for a fixed boolean conjunctive query q\, testing whether q is certain for
  an input database D is either polynomial time or coNP-complete.\n\nThe co
 njecture is open in general\, but has been verified for self-join-free and
  path queries. However\, the polynomial time algorithms known in the liter
 ature are complex and use different strategies in the two cases.  We propo
 se a simple inflationary fixpoint algorithm for consistent query answering
  which  correctly computes certain answers when the query q falls in the p
 olynomial time cases for self-join-free queries and path queries.  This ra
 ises a natural question\, whether this algorithm works for all polynomial 
 time cases. We answer this negatively and show that there are polynomial t
 ime certain queries (with self-joins) which cannot be computed by such an 
 algorithm. These results were obtained in collaboration with Diego Figueir
 a\, Luc Segoufin and Cristina Sirangelo and will be presented at ICDT'23.
 \n\nWe will also discuss some ongoing work on the conjecture for queries w
 ith self-joins over two atoms.\nhttps://ratio.labri.fr/#meetings
DTSTART;TZID=Europe/Paris:20230214T140000
DTEND;TZID=Europe/Paris:20230214T150000
LOCATION:178
SEQUENCE:0
SUMMARY:[RATIO] Anantha Padmanabha
TRANSP:OPAQUE
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