Semantically Acyclic Conjunctive Queries under Functional Dependencies

Diego Figueira (1)

1 CNRS - Centre National de la Recherche Scientifique

The evaluation problem for Conjunctive Queries (CQ) is known to be NP-complete in combined complexity and W[1]-hard in param-eterized complexity. However, acyclic CQs and CQs of bounded tree-width can be evaluated in polynomial time in combined complexity and they are fixed-parameter tractable. We study the problem of whether a CQ can be rewritten into an equivalent CQ of bounded tree-width, in the presence of unary functional dependencies, assuming bounded arity signatures. We show that this problem is decidable in doubly exponential time, or in exponential time for a subclass of CQ's. When it exists, the algorithm also yields a witness query.

Domaines: Base de données [cs.DB]; Théorie et langage formel [cs.FL]; Mathématique discrète [cs.DM]; Logique en informatique [cs.LO]

Diego Figueira. Semantically Acyclic Conjunctive Queries under Functional Dependencies. Annual ACM/IEEE Symposium on Logic in Computer Science (LICS), Jul 2016, New York, United States. ⟨10.1145/2933575.2933580⟩. ⟨hal-01713329v2⟩