Definability problems in elementary topology
Mariko Yasugi · Journal of the Australian Mathematical Society Series A Pure Mathematics and Statistics · 1983
Abstract The elementary part of general topology is carried out in a system which is based on the arithmetically definable theory of the reals with definitions by definable induction (DDI), where a formal object is said to be definable if the quantifiers are restricted to the rationals, the names of the base members and the elements of the spaces.