Publication at Faculty of Mathematics and Physics |
2021
Abstract
We prove that relational structures admitting specific polymorphisms (namely, canonical pseudoWNU operations of all arities n >= 3) have low relational width. This implies a collapse of the bounded width hierarchy for numerous classes of infinite-domain CSPs studied in the literature.
Moreover, we obtain a characterization of bounded width for first-order reducts of unary structures and a characterization of MMSNP sentences that are equivalent to a Datalog program, answering a question posed by Bienvenu et al.. In particular, the bounded width hierarchy collapses in those cases as well.