Mottet, AntoineAntoineMottetNagy, TomášTomášNagyPinsker, MichaelMichaelPinskerWrona, MichałMichałWrona2022-03-222022-03-222021-0748th International Colloquium on Automata, Languages, and Programming (ICALP 2021) 198: 138 (2021)http://hdl.handle.net/11420/12070We prove that relational structures admitting specific polymorphisms (namely, canonical pseudo- WNU 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.enBounded widthConstraint satisfaction problemsLocal consistencyPolymorphismsSmooth approximationsConference Paper10.4230/LIPIcs.ICALP.2021.138Conference Paper