- ZF
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1995 University of Cambridge Zermelo-Fraenkel Set Theory. This theory is the work of Martin Coen, Philippe Noel and Lawrence Paulson. Isabelle/ZF formalizes the greater part of elementary set theory, including relations, functions, injections, surjections, ordinals and cardinals. Results proved include Cantor's Theorem, the Recursion Theorem, the Schroeder-Bernstein Theorem, and (assuming AC) the Wellordering Theorem. Isabelle/ZF also provides theories of lists, trees, etc., for formalizing computational notions. It supports inductive definitions of infinite-branching trees for any cardinality of branching. Useful references for Isabelle/ZF: Lawrence C. Paulson, Set theory for verification: I. From foundations to functions. J. Automated Reasoning 11 (1993), 353-389. Lawrence C. Paulson, Set theory for verification: II. Induction and recursion. Report 312, Computer Lab (1993). Lawrence C. Paulson, A fixedpoint approach to implementing (co)inductive definitions. In: A. Bundy (editor), CADE-12: 12th International Conference on Automated Deduction, (Springer LNAI 814, 1994), 148-161. Useful references on ZF set theory: Paul R. Halmos, Naive Set Theory (Van Nostrand, 1960) Patrick Suppes, Axiomatic Set Theory (Dover, 1972) Keith J. Devlin, Fundamentals of Contemporary Set Theory (Springer, 1979) Kenneth Kunen, Set Theory: An Introduction to Independence Proofs, (North-Holland, 1980)

- ZF-AC
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1995 University of Cambridge Proofs of AC-equivalences, due to Krzysztof Grabczewski. See also the book "Equivalents of the Axiom of Choice, II" by H. Rubin and J.E. Rubin, 1985. The report http://www.cl.cam.ac.uk/Research/Reports/TR377-lcp-mechanising-set-theory.ps.gz "Mechanizing Set Theory", by Paulson and Grabczewski, describes both this development and ZF's theories of cardinals.

- ZF-Coind
Author: Jacob Frost, Cambridge University Computer Laboratory Copyright 1995 University of Cambridge Coind -- A Coinduction Example. It involves proving the consistency of the dynamic and static semantics for a small functional language. A codatatype definition specifies values and value environments in mutual recursion: non-well-founded values represent recursive functions; value environments are variant functions from variables into values. Based upon the article Robin Milner and Mads Tofte, Co-induction in Relational Semantics, Theoretical Computer Science 87 (1991), pages 209-220. Written up as Jacob Frost, A Case Study of Co_induction in Isabelle Report, Computer Lab, University of Cambridge (1995). http://www.cl.cam.ac.uk/Research/Reports/TR359-jf10008-co-induction-in-isabelle.dvi.gz

- ZF-Constructible
Relative Consistency of the Axiom of Choice: Inner Models, Absoluteness and Consistency Proofs. GĂ¶del's proof of the relative consistency of the axiom of choice is mechanized using Isabelle/ZF. The proof builds upon a previous mechanization of the reflection theorem (see http://www.cl.cam.ac.uk/users/lcp/papers/Sets/reflection.pdf). The heavy reliance on metatheory in the original proof makes the formalization unusually long, and not entirely satisfactory: two parts of the proof do not fit together. It seems impossible to solve these problems without formalizing the metatheory. However, the present development follows a standard textbook, Kunen's Set Theory, and could support the formalization of further material from that book. It also serves as an example of what to expect when deep mathematics is formalized. A paper describing this development is http://www.cl.cam.ac.uk/TechReports/UCAM-CL-TR-551.pdf

- ZF-IMP
Author: Heiko Loetzbeyer & Robert Sandner, TUM Copyright 1994 TUM Formalization of the denotational and operational semantics of a simple while-language, including an equivalence proof. The whole development essentially formalizes/transcribes chapters 2 and 5 of Glynn Winskel. The Formal Semantics of Programming Languages. MIT Press, 1993.

- ZF-Induct
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 2001 University of Cambridge Inductive definitions.

- ZF-Resid
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1995 University of Cambridge Residuals -- a proof of the Church-Rosser Theorem for the untyped lambda-calculus. By Ole Rasmussen, following the Coq proof given in Gerard Huet. Residual Theory in Lambda-Calculus: A Formal Development. J. Functional Programming 4(3) 1994, 371-394. See Rasmussen's report: The Church-Rosser Theorem in Isabelle: A Proof Porting Experiment. http://www.cl.cam.ac.uk/ftp/papers/reports/TR364-or200-church-rosser-isabelle.ps.gz

- ZF-UNITY
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1998 University of Cambridge ZF/UNITY proofs.

- ZF-ex
Author: Lawrence C Paulson, Cambridge University Computer Laboratory Copyright 1993 University of Cambridge Miscellaneous examples for Zermelo-Fraenkel Set Theory. Includes a simple form of Ramsey's theorem. A report is available: http://www.cl.cam.ac.uk/Research/Reports/TR271-lcp-set-theory.dvi.Z Several (co)inductive and (co)datatype definitions are presented. The report http://www.cl.cam.ac.uk/Research/Reports/TR312-lcp-set-II.ps.gz describes the theoretical foundations of datatypes while href="http://www.cl.cam.ac.uk/Research/Reports/TR320-lcp-isabelle-ind-defs.dvi.gz describes the package that automates their declaration.