Z, pronounced "zed", is a formal specification notation, a notation for formally, mathematically specifying, describing, computer-based systems. It is not a programming language, so it has no compiler as such, but many tools exist: type-checkers, animators for Z subsets, proof tools, more. Z is based on Zermelo-Fraenkel set theory and first order predicate logic. Inspired by the work of Jean-Raymond Abrial, it has been developed by the Programming Research Group (PRG) at the Oxford University Computing Laboratory (OUCL), and elsewhere, since the late 1970s. It is public domain, under ISO/IEC Z Standard 13568:2002, and Z symbols are part of Unicode character encoding.