Work

Extremal Fitting Problems for Conjunctive Queries

Year: 2026

Type: article

Abstract: The fitting problem for conjunctive queries (CQs) is the problem to construct a CQ that fits a given set of labeled data examples. When a fitting CQ exists, it is in general not unique. This leads us to propose natural refinements of the notion of a fitting CQ, such as most-general fitting CQ , most-specific fitting CQ , and unique fitting CQ . We give structural characterizations of these notions in terms of (suitable refinements of) homomorphism dualities, frontiers, and direct products, which enable the construction of the refined fitting CQs when they exist. We also pinpoint the complexity of the associated existence and verification problems, and determine the size of fitting CQs. We study the same problems for unions of CQs (UCQs).

Source: Journal of the ACM

DOI: 10.1145/3858670

Authors: Balder ten Cate, Victor Dalmau, Maurice Funk, Carsten Lutz

Institutions: University of Amsterdam, Universitat Pompeu Fabra, Leipzig University

Language: English

Topic: Advanced Database Systems and Queries

Subfield: Computer Networks and Communications

Field: Computer Science

Domain: Physical Sciences

Open Access status: hybrid

Funders: European Commission, Deutscher Akademischer Austauschdienst, Deutsche Forschungsgemeinschaft, Bundesministerium für Bildung und Forschung

Awards: G4712284355, Logic and Learning: an Algebra and Finite-Model-Theory Approach