Campus Event Calendar: Sergey Paramonov (05/07/2012 in E1 4/024)

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Event Entry

What and Who

Query Completeness: A Logic Programming Approach

Sergey Paramonov

Vienna University of Technology – Austria

PhD Application Talk

AG 1, AG 2, AG 3, AG 4, AG 5, SWS, RG1, MMCI

Public Audience

English

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Date, Time and Location

Monday, 7 May 2012

09:20

60 Minutes

E1 4

024

Saarbrücken

Abstract

How to manage incomplete information has been studied in database research almost from the beginning. The focus was on how to represent incomplete information and how to compute certain answers. Less attention has been given to describing which parts of a database are complete and how to find out whether a query returns complete answers over a partially complete database. To address these questions, we build on previous work by Motro (1989) and Levy (1995) who formalized when a query is complete over a partially complete database and what it means that parts of the tables are complete. Recently, Razniewski and Nutt (2011) characterized the complexity of various reasoning tasks in this setting. It was open, however, how to implement completeness reasoners in practice.

In this talk, we introduce the problem of query completeness reasoning and show that it can be mapped elegantly to answer set programming (ASP) over datalog with negation. Then we consider extensions of the original problem that take into account foreign key constraints and finite domain constraints on attributes. To encode the extensions, we make use of Skolem functions and of datalog rules with disjunctions in the head. We show the correctness and completeness of the encodings by several characterization theorems.

With our encodings we can solve completeness reasoning tasks using the DLV system, which implements answer set programming for disjunctive logic programs. DLV is being developed at TU Vienna and at the U of Calabria.

Joint work with Werner Nutt and Ognjen Savkovic (FU Bozen-Bolzano)

Contact

IMPRS-Office Team

9325 1800

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Marc Schmitt, 05/04/2012 13:38 -- Created document.

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