New Results for the Complexity of Resilience for Binary Conjunctive Queries with Self-Joins

Freire, Cibele; Gatterbauer, Wolfgang; Immerman, Neil; Meliou, Alexandra

doi:10.1145/3375395.3387647

Cited by 8 publications

(1 citation statement)

References 36 publications

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“…However, for path queries q with self-joins, CERTAINTY(q) exhibits a tetrachotomy between FO, NL-complete, PTIME-complete, and coNP-complete [32], and the complexity classification requires sophisticated tools. Note incidentally that self-join-freeness is a simplifying assumption that is also frequent outside CQA (e.g., [20,5,21,1]).…”

Section: Introductionmentioning

confidence: 99%

Consistent Query Answering for Primary Keys on Path Queries

Koutris

Ouyang

Wijsen

2021

Proceedings of the 40th ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems

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We study the data complexity of consistent query answering (CQA) on databases that may violate the primary key constraints. A repair is a maximal subset of the database satisfying the primary key constraints. For a Boolean query q, the problem CERTAINTY(q) takes a database as input, and asks whether or not each repair satisfies q. The computational complexity of CERTAINTY(q) has been established whenever q is a selfjoin-free Boolean conjunctive query, or a (not necessarily self-join-free) Boolean path query. In this paper, we take one more step towards a general classification for all Boolean conjunctive queries by considering the class of rooted tree queries. In particular, we show that for every rooted tree query q, CERTAINTY(q) is in FO, NL-hard ∩ LFP, or coNP-complete, and it is decidable (in polynomial time), given q, which of the three cases applies. We also extend our classification to larger classes of queries with simple primary keys. Our classification criteria rely on query homomorphisms and our polynomial-time fixpoint algorithm is based on a novel use of context-free grammar (CFG).

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