A Special Issue on Formal Proof
Using computers in proofs both extends mathematics with new results and creates new mathematical questions about the nature and technique of such proofs. This special issue features a collection of articles by practitioners and theorists of such formal proofs which explore both aspects.
(pp. 1363)
Thomas Hales
(pp. 1370)
Formal Proof--The Four-Color Theorem
Georges Gonthier
(pp. 1382)
Formal Proof--Theory and Practice
John Harrison
(pp. 1395)
Formal Proof--Getting Started
Freek Wiedijk
By Julie Rehmeyer
Web edition : Friday, November 14th, 2008
Mathematicians develop computer proof-checking systems in order to realize century-old dreams of fully precise, accurate mathematics.
In my experience, proof readers tend to be rather calm individuals, going about their work in an unruffled, dignified manner. Proof readers are rarely confrontational in temperament, because proofreading by its very nature requires a serene and reflective approach. So, it was rare for me, as an Operations Manager supervising, amongst other people, proof readers, to have to intervene in any kind of serious dispute.
Except when it came to hyphens.
Vampire is winning at least one division of the world cup in theorem proving CASC since 1999. All together Vampire won 17 titles: more than any other prover. We traditionally take part in the following two divisions of the competition: * The FOF division: unrestricted first-order problems. This division was ranked second in importance after the MIX division before 2007 and is now recognised as the main competition division. * The CNF division: first-order problems in conjunctive normal form. This division was called MIX before 2007 and recognised as the main competition division. We also participate in other, more special competition divisions but Vampire is not specialised for them so our achievements are mostly modest.
This site is an experimental HTML rendering of fragments of the IsarMathLib project. IsarMathLib is a library of mathematical proofs formally verified by the Isabelle theorem proving environment. The formalization is based on the Zermelo-Fraenkel set theory. The Introduction provides more information about IsarMathLib. The software for exporting Isabelle's Isar language to HTML markup is at an early beta stage, so some proofs may be rendered incorrectly. In case of doubts, compare with the Isabelle generated IsarMathLib proof document.
In the fully expansive (or LCF-style) approach to theorem proving, theorems are represented by an abstract type whose primitive operations are the axioms and inference rules of a logic. Theorem proving tools are implemented by composing together the inference rules using ML programs. This idea can be generalised to computing valid judgements that represent other kinds of information. In particular, consider judgements (a,r,t,b), where a is a set of boolean terms (assumptions) that are assumed true, r represents a variable order, t is a boolean term all of whose free variables are boolean and b is a BDD. Such a judgement is valid if under the assumptions a, the BDD representing t with respect to r is b, and we will write a r t --> b when this is the case. The derivation of "theorems" like a r t --> b can be viewed as "proof" in the style of LCF by defining an abstract type term_bdd that models judgements a r t --> b analogously to the way the type thm models theorems |- t.
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ProofWeb is both a system for teaching logic and for using proof assistants through the web.
ProofWeb can be used in three ways. First, one can use the guest login, for which one does not even need to register. Secondly, a user can be a student in a logic or proof assistants course. We are hosting courses free of charge. If you are a teacher and would like to host your course on this server, send email to proofweb@cs.ru.nl. Thirdly, if teachers do not want to trust us with their students' files, they can freely download the ProofWeb system and run it on a server of their own.
IsaPlanner is a generic framework for proof planning in the interactive theorem prover Isabelle. It facilitates the encoding of reasoning techniques, which can be used to conjecture and prove theorems automatically. The system provides an interactive tracing tool that allows you to interact the proof planning attempt. (see the screenshot of IsaPlanner being used with Isabelle and Proof General) It is based on the Isabelle theorem prover and the Isar language. The main proof technique written in IsaPlanner is an inductive theorem prover based on Rippling. This is applicable within Isabelle's Higher Order Logic, and can easily be adapted to Isabelle's other logics. The system now the main platform for proof planning research in the Edinburgh mathematical reasoning group
HOL4 is the latest version of the HOL interactive proof assistant for higher order logic: a programming environment in which theorems can be proved and proof tools implemented. Built-in decision procedures and theorem provers can automatically establish many simple theorems (users may have to prove the hard theorems themselves!) An oracle mechanism gives access to external programs such as SAT and BDD engines. HOL 4 is particularly suitable as a platform for implementing combinations of deduction, execution and property checking. several widely used versions of the HOL system: 1. HOL88 from Cambridge; 2. HOL90 from Calgary and Bell Labs; 3. HOL98 from Cambridge, Glasgow and Utah. HOL 4 is the successor to these. Its development was partly supported by the PROSPER project. HOL 4 is based on HOL98 and incorporates ideas and tools from HOL Light. The ProofPower system is another implementation of HOL.
F. Arzarello. the 24th Conference of the International Group for the Psychology of Mathematics Education (PME), 1, page 23--38. Hiroshima, Japan, (2000)