2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/31733This paper addresses the question whether one can determine the connectivity of a semi-algebraic set in three dimensions by testing the connectivity of a finite number of two-dimensional ``samples'' of the set, where these samples are defined by first-order queries. The question is answered negatively for two classes of first-order queries: cartesian-product-free, and positive one-pass.corrected minor confusion in Proof of Theorem 1Logic in Computer ScienceComputational GeometryDatabasesF.4.1; F.2.2; H.2.8text