Search Results for author: Reinhard Pichler

Found 5 papers, 3 papers with code

The HyperTrac Project: Recent Progress and Future Research Directions on Hypergraph Decompositions

no code implementations29 Dec 2020 Georg Gottlob, Matthias Lanzinger, Davide Mario Longo, Cem Okulmus, Reinhard Pichler

Constraint Satisfaction Problems (CSPs) play a central role in many applications in Artificial Intelligence and Operations Research.

HyperBench: A Benchmark and Tool for Hypergraphs and Empirical Findings

1 code implementation2 Sep 2020 Wolfgang Fischl, Georg Gottlob, Davide Mario Longo, Reinhard Pichler

To cope with the intractability of answering Conjunctive Queries (CQs) and solving Constraint Satisfaction Problems (CSPs), several notions of hypergraph decompositions have been proposed -- giving rise to different notions of width, noticeably, plain, generalized, and fractional hypertree width (hw, ghw, and fhw).

HyperBench: A Benchmark and Tool for Hypergraphs and Empirical Findings

1 code implementation20 Nov 2018 Wolfgang Fischl, Georg Gottlob, Davide M. Longo, Reinhard Pichler

To cope with the intractability of answering Conjunctive Queries (CQs) and solving Constraint Satisfaction Problems (CSPs), several notions of hypergraph decompositions have been proposed -- giving rise to different notions of width, noticeably, plain, generalized, and fractional hypertree width (hw, ghw, and fhw).

Databases

Datalog: Bag Semantics via Set Semantics

no code implementations17 Mar 2018 Leopoldo Bertossi, Georg Gottlob, Reinhard Pichler

This use of Datalog$^\pm$ is extended to give a set semantics to duplicates in Datalog$^\pm$ itself.

Translation

General and Fractional Hypertree Decompositions: Hard and Easy Cases

2 code implementations3 Nov 2016 Wolfgang Fischl, Georg Gottlob, Reinhard Pichler

It is known that hw(H) <= k can be checked in polynomial time for fixed k, while checking ghw(H) <= k is NP-complete for any k greater than or equal to 3.

Databases Computational Complexity

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