A pointclass is a collection of subsets of topological spaces, usually specified by a common definability or closure condition.
An analytic subset of a Polish space is a continuous image of a Borel set, equivalently a projection of a closed subset of its product with the Baire space of sequences.
The projective hierarchy starts with the Borel sets and repeatedly applies projection and complementation. Its members are the projective sets.
Articles by others on the same topic
"Pointclass" is not a widely recognized term in common usage, and it might refer to different things in various contexts. It could pertain to a specific software tool, framework, or concept within a certain field such as programming, data science, or mathematics. For example, in programming contexts, "Pointclass" might refer to a class in object-oriented programming that represents a point in a Cartesian coordinate system, typically containing properties like x and y coordinates.