A characterization of first-order topological properties of planar spatial data
Michael Benedikt, Bart Kuijpers, Christof Löding, Jan Van den Bussche, Thomas Wilke · Journal of the ACM · 2006
Planar spatial datasets can be modeled by closed semi-algebraic sets in the plane. We establish a characterization of the topological properties of such datasets expressible in the relational calculus with real polynomial constraints. The characterization is in the form of a query language that can only point that can only talk about points in the set and the “cones” around these points.