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<h2>What is Isabelle?</h2>
<p>
Isabelle is a popular generic theorem proving environment
developed at Cambridge University (<a
href="http://www.cl.cam.ac.uk/users/lcp/">Larry Paulson</a>)
and TU Munich (<a href="http://www.in.tum.de/~nipkow/">Tobias
Nipkow</a>). See the <a href="overview.html">Isabelle
overview</a>.
</p>
<p>
These site provides general information on Isabelle, more
specific information is available from the local sites
</p>
<ul>
<li><a href="http://www.cl.cam.ac.uk/Research/HVG/Isabelle/cambridge.html"><strong>Isabelle
at Cambridge</strong></a></li>
<li><a href="http://www4.in.tum.de/proj/theoremprov/group.html"><strong>Isabelle
at Munich</strong></a></li>
</ul>
<p>
See there for information on projects done with Isabelle,
mailing list archives, research papers, the Isabelle
bibliography, and Isabelle workshops and courses.
</p>
<h2>Coming soon: Isabelle 2005</h2>
<p>New features in the upcoming Isabelle 2005 will include</p>
<ul>
<li>New commands for instantiating locales</li>
<li>New command for finding theorems (by term patterns, as intro/elim/simp rules, etc.)</li>
<li>New automatic transitivity reasoner</li>
<li>New command for ad-hoc theory viewing and printing</li>
<li>Much extended and improved theory of finite sets</li>
<li>New syntax that will allow > and >= in addition to < and
<=</li>
</ul>
<h2>Isabelle 2004</h2>
<p>New features in Isabelle 2004 include</p>
<ul>
<li>New image HOL4 with imported library from HOL4 system on top of
HOL-Complex (about 2500 additional theorems).</li>
<li>New theory Ring_and_Field with over 250 basic numerical laws,
all proved in axiomatic type classes for semirings, rings and fields.</li>
<li>New locale <code>ring</code> for non-commutative rings in HOL-Algebra.</li>
<li>Type <code>rat</code> of the rational numbers available in HOL-Complex.</li>
<li>New theory of matrices with an application to linear programming in HOL-Matrix.</li>
<li>Improved locales (named proof contexts), instantiation of locales.</li>
<li>Improved handling of linear and partial orders in simplifier.</li>
<li>New <code>specification</code> command for definition by specification.</li>
<li>New Isar command <code>finalconsts</code> prevents constants being given a definition later.</li>
<li><code>arith</code> now generates counterexamples for reals as well.</li>
<li>New <code>quickcheck</code> command
to search for counterexamples of executable goals.
(see HOL/ex/Quickcheck_Examples.thy)</li>
<li>New <code>refute</code> command
to search for finite countermodels of goals.
(see HOL/ex/Refute_Examples.thy)
</li>
<li>Presentation and x-symbol enhancements, greek letters and
sub/superscripts allowed in identifiers.</li>
</ul>
<p><a href="//dist/packages/Isabelle/NEWS">[Complete Changelog]</a></p>
<h2>Download</h2>
<p>
The Isabelle distribution is distributed <em>for free</em> and available
from several <a href="mirrors.html">mirror sites</a>. It includes
source and binary packages and browsable documentation. You can also
browse the <a href="//library/index.html">Isabelle theory library</a>
online.
</p>
<p>
Use the mailing list <a href=
"mailto:isabelle-users@cl.cam.ac.uk">isabelle-users@cl.cam.ac.uk</a> and its
<a href="http://www.cl.cam.ac.uk/users/lcp/archive/">archive</a> to
discuss problems and results. To subscribe, <a href=
"mailto:Cl-isabelle-users-request@lists.cam.ac.uk?subject=subscribe">
contact our robot</a>.
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