Right-Adjoints for Datalog Programs

Authors Balder ten Cate , Víctor Dalmau , Jakub Opršal

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Author Details

Balder ten Cate
  • Institute for Logic, Language, and Computation, University of Amsterdam, The Netherlands
Víctor Dalmau
  • Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain
Jakub Opršal
  • School of Computer Science, University of Birmingham, UK


Thanks to Pierre Bourrhis for detailed feedback and catching mistakes.

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Balder ten Cate, Víctor Dalmau, and Jakub Opršal. Right-Adjoints for Datalog Programs. In 27th International Conference on Database Theory (ICDT 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 290, pp. 10:1-10:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)


A Datalog program can be viewed as a syntactic specification of a mapping from database instances over some schema to database instances over another schema. We establish a large class of Datalog programs for which this mapping admits a (generalized) right-adjoint. We employ these results to obtain new insights into the existence of, and methods for constructing, homomorphism dualities within restricted classes of instances. From this, we derive new results regarding the existence of uniquely characterizing data examples for database queries in the presence of integrity constraints.

Subject Classification

ACM Subject Classification
  • Theory of computation → Logic and databases
  • Datalog
  • Adjoints
  • Homomorphism Dualities
  • Database Constraints
  • Conjunctive Queries
  • Data Examples


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