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.
@InProceedings{tencate_et_al:LIPIcs.ICDT.2024.10, author = {ten Cate, Balder and Dalmau, V{\'\i}ctor and Opr\v{s}al, Jakub}, title = {{Right-Adjoints for Datalog Programs}}, booktitle = {27th International Conference on Database Theory (ICDT 2024)}, pages = {10:1--10:20}, series = {Leibniz International Proceedings in Informatics (LIPIcs)}, ISBN = {978-3-95977-312-6}, ISSN = {1868-8969}, year = {2024}, volume = {290}, editor = {Cormode, Graham and Shekelyan, Michael}, publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik}, address = {Dagstuhl, Germany}, URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICDT.2024.10}, URN = {urn:nbn:de:0030-drops-197929}, doi = {10.4230/LIPIcs.ICDT.2024.10}, annote = {Keywords: Datalog, Adjoints, Homomorphism Dualities, Database Constraints, Conjunctive Queries, Data Examples} }
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