%0 Journal Article %T Two- versus three-dimensional connectivity testing of first-order queries to semi-algebraic sets %A Floris Geerts %A Lieven Smits %A Jan Van den Bussche %J Computer Science %D 2003 %I arXiv %R 10.1007/s00236-005-0171-5 %X This 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. %U http://arxiv.org/abs/cs/0308001v2