Paper Info
Title
Consistent Query Answering for Primary Keys in Logspace.
Abstract
We study the complexity of consistent query answering on databases that may violate primary key constraints. A repair of such a database is any consistent database that can be obtained by deleting a minimal set of tuples. For every Boolean query q, CERTAINTY(q) is the problem that takes a database as input and asks whether q evaluates to true on every repair. In [KW17], the authors show that for every self-join-free Boolean conjunctive query q, the problem CERTAINTY(q) is either in P or coNP-complete, and it is decidable which of the two cases applies. In this paper, we sharpen this result by showing that for every self-join-free Boolean conjunctive query q, the problem CERTAINTY(q) is either expressible in symmetric stratified Datalog or coNP-complete. Since symmetric stratified Datalog is in L, we thus obtain a complexity-theoretic dichotomy between L and coNP-complete. Another new finding of practical importance is that CERTAINTY(q) is on the logspace side of the dichotomy for queries q where all join conditions express foreign-to-primary key matches, which is undoubtedly the most common type of join condition.
Year
Venue
Field
2018
ICDT 2019
Computer science,Theoretical computer science
DocType
Volume
Citations 
Journal
abs/1810.03386
0
PageRank 
References 
Authors
0.34
0
2
Name
Order
Citations
PageRank
Paraschos Koutris134726.63
Jef Wijsen267895.21