Isabelle 2005

Isabelle is a popular generic theorem prover developed at Cambridge University and TU Munich. Isabelle is a generic proof assistant. It allows mathematical formulas to be expressed in a formal language and provides tools for proving those formulas in a logical calculus. The main application is the formalization of mathematical proofs and in particular formal verification, which includes proving the correctness of computer hardware or software and proving properties of computer languages and protocols.
Compared with similar tools, Isabelles distinguishing feature is its flexibility. Most proof assistants are built around a single formal calculus, typically higher-order logic. Isabelle has the capacity to accept a variety of formal calculi. The distributed version supports higher-order logic but also axiomatic set theory and several other formalisms. See logics for more details.
Isabelle is a joint project between Lawrence C. Paulson (University of Cambridge, UK) and Tobias Nipkow (Technical University of Munich, Germany).
Main features:
- Interpretation of locale expressions in theories, locales, and proof contexts.
- Substantial library improvements (HOL, HOL-Complex, HOLCF).
- Proof tools for transitivity reasoning.
- General find_theorems command (by term patterns, as intro/elim/simp rules etc.).
- Commands for generating adhoc draft documents.
- Support for Unicode proof documents (UTF-8).
- Major internal reorganizations and performance improvements.