,
Žaneta Semanišinová
Creative Commons Attribution 4.0 International license
We prove a complexity dichotomy for the resilience problem for unions of conjunctive digraph queries (i.e., for existential positive sentences over the signature {R} of directed graphs). Specifically, for every union μ of conjunctive digraph queries, the following problem is in P or NP-complete: given a directed multigraph G and a natural number u, can we remove u edges from G so that G ⊧ ¬ μ? In fact, we verify a more general dichotomy conjecture from [Bodirsky et al., 2024] for all resilience problems in the special case of directed graphs, and show that for such unions of queries μ there exists a countably infinite (`dual') valued structure Δ_μ which either primitively positively constructs 1-in-3-3-SAT, and hence the resilience problem for μ is NP-complete by general principles, or has a pseudo cyclic canonical fractional polymorphism, and the resilience problem for μ is in P.
@InProceedings{bodirsky_et_al:LIPIcs.STACS.2026.15,
author = {Bodirsky, Manuel and Semani\v{s}inov\'{a}, \v{Z}aneta},
title = {{The Complexity of Resilience for Digraph Queries}},
booktitle = {43rd International Symposium on Theoretical Aspects of Computer Science (STACS 2026)},
pages = {15:1--15:20},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-412-3},
ISSN = {1868-8969},
year = {2026},
volume = {364},
editor = {Mahajan, Meena and Manea, Florin and McIver, Annabelle and Thắng, Nguy\~{ê}n Kim},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2026.15},
URN = {urn:nbn:de:0030-drops-255045},
doi = {10.4230/LIPIcs.STACS.2026.15},
annote = {Keywords: valued constraints, unions of conjunctive queries, resilience, computational complexity, pp-constructions}
}