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7 <title>Overview</title> |
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17 <h2>What is Isabelle?</h2> |
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18 <p> |
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19 Isabelle is a generic proof assistant. It allows mathematical |
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20 formulas to be expressed in a formal language and provides tools |
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21 for proving those formulas in a logical calculus. The main |
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22 application is the formalization of mathematical proofs and in |
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23 particular <em>formal verification</em>, which includes proving |
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24 the correctness of computer hardware or software and proving |
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25 properties of computer languages and protocols.</p> |
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26 |
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27 <p>Compared with similar tools, Isabelle's distinguishing feature is its |
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28 flexibility. Most proof assistants are built around a single formal calculus, |
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29 typically higher-order logic. Isabelle has the capacity to accept a variety |
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30 of formal calculi. The distributed version supports higher-order logic but |
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31 also axiomatic set theory and several other formalisms. See |
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32 <a href="logics.html">logics</a> for more details.</p> |
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33 |
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34 <p>Isabelle is a joint project between Lawrence C. Paulson |
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35 (University of Cambridge, UK) and Tobias Nipkow (Technical |
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36 University of Munich, Germany).</p> |
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37 |
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38 <h2>What Isabelle offers</h2> |
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39 |
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40 <a href="//img/isabelle_pg_screenshot_big.png"> |
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41 <img class="left" src="//img/isabelle_pg_screenshot_small.png" alt="Sreenshot " |
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43 </a> |
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44 |
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45 <p>Isabelle provides excellent notational support: new notations |
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46 can be introduced, using normal mathematical symbols. Proofs can |
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47 be written in a structured notation based upon traditional proof |
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48 style, or more straightforwardly as sequences of |
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49 commands. Definitions and proofs may include TeX source, from |
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50 which Isabelle can automatically generate typeset documents.</p> |
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51 |
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52 <p>The main limitation of all such proof systems is that proving |
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53 theorems requires much effort from an expert user. Isabelle |
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54 incorporates some tools to improve the user's productivity by |
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55 automating some parts of the proof process. In particular, |
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56 Isabelle's <em>classical reasoner</em> can perform long chains |
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57 of reasoning steps to prove formulas. The <em>simplifier</em> |
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58 can reason with and about equations. Linear <em>arithmetic</em> |
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59 facts are proved automatically.</p> |
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60 |
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61 <p>Isabelle comes with a large theory library of formally |
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62 verified mathematics, including elementary number theory (for |
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63 example, Gauss's law of quadratic reciprocity), analysis (basic |
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64 properties of limits, derivatives and integrals), algebra (up to |
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65 Sylow's theorem) and set theory (the relative consistency of the |
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66 Axiom of Choice). Also provided are numerous examples arising |
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67 from research into formal verification.</p> |
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68 |
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69 <p>With <em>Isar</em>, Isabelle offers a concise proof formulation language |
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70 which enables a user to write proof scripts naturally understandable for |
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71 both humans <em>and</em> computers.</p> |
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72 |
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73 <p>Isabelle is closely integrated with the <a href= |
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74 "http://proofgeneral.inf.ed.ac.uk/">ProofGeneral</a> user interface, which |
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75 eases the task of writing and maintaining proof scripts.</p> |
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76 <br clear="both" /> |
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77 |
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78 <h2>Preview</h2> |
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79 |
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80 <p>We provide a <a href="PG-preview.mov">hyperlinked preview</a> demonstrating |
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81 Isabelle and ProofGeneral, in <a href="http://www.apple.com/quicktime/download/">QuickTime |
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82 format</a>, and also as a <a href="PG-preview.pdf">non-hyperlinked preview</a> in PDF.</p> |
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83 |
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84 <p>Ample <a href="dist/documentation.html">documentation</a> is available |
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85 about using Isabelle and its inner concepts, including a |
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86 <a href="http://www4.in.tum.de/~nipkow/LNCS2283/">Tutorial</a> published by |
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87 Springer-Verlag.</p> |
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88 |
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89 <h2>Projects</h2> |
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90 |
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91 <p>There is an (incomplete) list of past and present <a href= |
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92 "http://www.cl.cam.ac.uk/Research/HVG/Isabelle/projects.html">projects</a> |
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93 undertaken using Isabelle available.</p> |
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94 |
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95 <h2>License</h2> |
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96 |
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97 <p>Isabelle is distributed free of charge under the open source |
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98 <a href="dist/Isabelle/COPYRIGHT">BSD license</a>. You may use any of our <a |
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99 href="dist/index.html">mirrors</a> for download.</p> |
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100 |
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101 </div> |
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102 <div class="hr"><hr/></div> |
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