<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <title>The Isabelle Logo</title></head><body><h1>The Isabelle Logo</h1><h2>Versions</h2>The logo is available as bitmap file for the generic Isabelle system(<a href="#plain">plain</a>, <a href="#transparent">transparent</a>)and major object logics (<a href="#ZF">ZF</a>, <a href="#HOL">HOL</a>,<a href="#HOLCF">HOLCF</a>). There are also <ahref="isabelle-small.xpm">small</a> and <ahref="isabelle-tiny.xpm">tiny</a> Isabelle icons available.Furthermore, scalable (EPS) versions of the logo may be generated forany logic using the <tt>isabelle logo</tt> utility distributed withIsabelle.<h2>Interpretation</h2><img src="isabelle.gif" align=right alt="[Isabelle logo]"> First ofall, the logo tells about the name of the generic system, Isabelle, orof its concrete instantiations, e.g. Isabelle/HOL. It also expressessome essentials of the overall Isabelle design philosophy: Compositionof several small well understood building blocks, grouped together orarranged in layers. <p>The markings on the cubes illustrate this general principle by exampleof the core meta-logic (which is minimal higher-order logic on top ofnaively polymorphic simply typed lambda calculus). Thus red cubessymbolize the type system with function spaces (->) and typevariables (alpha); violet ones represent the lambda term language withbeta conversion etc.; yellow cubes constitute the actual logicalparts, namely meta-implication or entailment (|-) and meta-leveluniversal quantification.<h2>Acknowledgment</h2>The logo is contributed by <ahref="http://www.informatik.tu-muenchen.de/~wenzel/">FranziskaWenzel</a>, Munich. It has been designed on Apple Macintosh.<p><hr><p><a name="plain"><img src="isabelle.gif" alt="[Isabelle logo]"></a> <p><a name="transparent"><img src="isabelle_transparent.gif" alt="[Isabelle logo (transparent)]"></a> Note: This may look bad onblack and white displays. <p><a name="ZF"><img src="isabelle_zf.gif" alt="[Isabelle logo (ZF)]"></a> <p><a name="HOL"><img src="isabelle_hol.gif" alt="[Isabelle logo (HOL)]"></a> <p><a name="HOLCF"><img src="isabelle_holcf.gif" alt="[Isabelle logo (HOLCF)]"></a></body></html>