2026-07-26T17:26:59Z https://drops.dagstuhl.de/oai

oai:drops-oai.dagstuhl.de:13717 2024-03-06T10:52:31Z ddc:004 open_access

Conjunctive Queries: Unique Characterizations and Exact Learnability ten Cate, Balder Dalmau, Victor Conjunctive Queries Homomorphisms Frontiers Unique Characterizations Exact Learnability Schema Mappings Description Logic We answer the question of which conjunctive queries are uniquely characterized by polynomially many positive and negative examples, and how to construct such examples efficiently. As a consequence, we obtain a new efficient exact learning algorithm for a class of conjunctive queries. At the core of our contributions lie two new polynomial-time algorithms for constructing frontiers in the homomorphism lattice of finite structures. We also discuss implications for the unique characterizability and learnability of schema mappings and of description logic concepts. Schloss Dagstuhl – Leibniz-Zentrum für Informatik Balder ten Cate and Victor Dalmau 2021 Is Part Of LIPIcs, Volume 186, 24th International Conference on Database Theory (ICDT 2021) InProceedings Text doc-type:ResearchArticle publishedVersion application/pdf doi:10.4230/LIPIcs.ICDT.2021.9 urn:nbn:de:0030-drops-137172 https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2021.9 eng https://creativecommons.org/licenses/by/4.0/legalcode