Editing Descriptive set theory (section)

== Effective descriptive set theory ==

The area of [[effective descriptive set theory]] combines the methods of descriptive set theory with those of [[generalized recursion theory]] (especially [[hyperarithmetical theory]]). In particular, it focuses on [[lightface]] analogues of hierarchies of classical descriptive set theory. Thus the [[hyperarithmetic hierarchy]] is studied instead of the Borel hierarchy, and the [[analytical hierarchy]] instead of the projective hierarchy.  This research is related to weaker versions of set theory such as [[Kripke–Platek set theory]] and [[second-order arithmetic]].