Ackermann bijection.; bisimulation; Computable set theory; non-well-founded sets; Information Systems; Computational Theory and Mathematics; Theoretical Computer Science; Algebra and Number Theory

Mapping Sets and Hypersets into Numbers

We introduce and prove the basic properties of encodings that generalize to non-well-founded hereditarily finite sets the bijection defined by Ackermann in 1937 between hereditarily finite sets and natural numbers.