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+ − 4 <TITLE>Homepage of Christian Urban</TITLE>
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+ − 37 <TD BGCOLOR="#FFFFFF"
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+ − 39 VALIGN="TOP"
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+ − 41
+ − 42 <B>Links</B><BR>
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+ − 43 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/index.html">Home</A><BR>
+ − 44 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/publications.html">Publications</A><BR>
+ − 45 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/teaching.html">Teaching</A><BR>
+ − 46 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/travelling.html">Recent Talks</A><BR>
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+ − 47 <A HREF="http://isabelle.in.tum.de/nominal/">My Research Group</A>
+ − 48 <BR>
+ − 49 <BR>
+ − 50
+ − 51 <B>Handy Information</B><BR>
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+ − 52 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/logic.html">People in Logic</A><BR>
+ − 53 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/programming.html">Programming Languages</A><BR>
+ − 54 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/misc.html">Miscellaneous</A>
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+ − 55 <BR><BR>
+ − 56
+ − 57 <A HREF="http://isabelle.in.tum.de/nominal/">
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+ − 58 <IMG SRC="nominal-logo.gif" ALT="" style="border-width: 0px;" align="left"></A>
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+ − 59 </TD>
+ − 60
+ − 61
+ − 62
+ − 63 <!-- right column -->
+ − 64 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 65 <A NAME="Home"></A>
+ − 66 <TABLE>
+ − 67 <TR>
+ − 68 <TD WIDTH="75%">
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+ − 69 <H1>Christian Urban</H1>
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+ − 70
+ − 71 <B>E-mail</B>
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+ − 72 christian.urban <I>at</I> kcl ac uk<BR>
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+ − 73 <BR>
+ − 74
+ − 75 <B>Address</B>
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+ − 76 <A HREF="http://www.inf.kcl.ac.uk">Department of Informatics</A>,
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+ − 77 <A HREF="http://www.kcl.ac.uk">King's College London</A>,
+ − 78 Strand, London WC2R 2LS, UK. My office is S6.30 on the 6th floor of the Strand Building.
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+ − 79 <BR><BR>
+ − 80
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+ − 81 <B>Fax</B> +44 20 7848 2851
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+ − 82 </TD>
+ − 83 <TD align="right" valign="top">
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+ − 84 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/picture-small.jpg"><IMG ALT="" SRC="picture-small.jpg" align="top"></A>
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+ − 85 </TD>
+ − 86 </TR>
+ − 87 </TABLE>
+ − 88 <p>
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+ − 89 <IMG SRC="new.gif" ALT="" style="" align="left"><A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Cookbook" target="_top">Isabelle Programming Tutorial</A> (draft of a 200-page tutorial on Isabelle programming)<BR>
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+ − 90 </TD>
+ − 91 </TR>
+ − 92
+ − 93 <TR>
+ − 94 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 95 <B>Current Position</B>
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+ − 96 I am a lecturer in the Department of Informatics at King's College London.
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+ − 97 This is similar to a position of an assistant professor in other places. In 2011,
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+ − 98 I was also offered a lectureship
+ − 99 <A HREF="http://www.it.uu.se/" TITLE="Uppsala">here</A>, an associate professorship
+ − 100 <A HREF="http://www.itu.dk/en/" TITLE="ITU, Copenhagen">here</A>,
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+ − 101 and full professorships
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+ − 102 <A HREF="http://www.ustcsz.edu.cn/kedweb/" TITLE="IAS, Suzhou">here</A> and
+ − 103 <A HREF="http://www.sei.ecnu.edu.cn/apps/portal/home.html" TITLE="Shanghai">here</A>.
+ − 104 I thank all people involved for their efforts.
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+ − 105 <P>
+ − 106
+ − 107 <B>Past Positions</B>
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+ − 108 In April 2006, I was awarded an <A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A>
+ − 109 <A HREF="http://www.dfg.de/en/research_funding/programmes/individual/emmy_noether/in_brief/index.html">fellowship</A>, which I held at the <A HREF="http://www.in.tum.de/en.html">TU Munich</A> until
+ − 110 September 2011.
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+ − 111 Between September 2008 and February 2009, I was an invited research fellow in
+ − 112 the <A HREF="http://www.cs.princeton.edu/">Department of Computer Science</A> in Princeton.
+ − 113 In 2004/05 I was an Alexander-von-Humboldt fellow in Munich and
+ − 114 from 2000 until 2004 I was awarded a Research Fellowship in Cambridge. Before that
+ − 115 I did my PhD in Cambridge.
+ − 116 <P>
+ − 117
+ − 118 <B>Research Interests</B> theorem provers, programming languages, compilers,
+ − 119 algorithms, proof theory, type systems, concurrency, lambda calculus, unification,
+ − 120 regular expressions, computability, complexity, functional and logic programming.
+ − 121 <P>
+ − 122
+ − 123 <B>Conferences</B>
+ − 124 <A HREF="http://www.iiia.csic.es/~levy/unif06/">UNIF'06</A> (member of PC),
+ − 125 <A HREF="http://www.cs.mcgill.ca/~bpientka/lfmtp07">LFMTP'07</A> (member of PC),
+ − 126 <A HREF="http://isabelle.in.tum.de/nominal/activities/lfmtp08/">LFMTP'08</A> (PC co-chair),
+ − 127 <A HREF="http://www.cis.upenn.edu/~sweirich/wmm/">WMM'08</A> (member of PC),
+ − 128 <A HREF="http://www.mat.ufmg.br/lsfa2008/">LSFA'08</A> (invited speaker),
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+ − 129 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/TAASN.html">TAASN'09</A> (member of PC),
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+ − 130 <A HREF="http://lsfa09.cic.unb.br/">LSFA'09</A> (member of PC),
+ − 131 <A HREF="http://isabelle.in.tum.de/nominal/activities/tphols09/idw.html">IDW'09</A> (organiser),
+ − 132 <A HREF="http://www.seas.upenn.edu/~sweirich/wmm/wmm09.html">WMM'09</A> (PC chair),
+ − 133 <A HREF="http://tphols.in.tum.de/">TPHOLs'09</A> (PC co-chair),
+ − 134 <A HREF="http://dream.inf.ed.ac.uk/events/automatheo-2010/">Automatheo'10</A> (member of PC),
+ − 135 <A HREF="http://www.floc-conference.org/">ITP'10</A> (member of PC),
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+ − 136 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/UNIF.html">UNIF'10</A> (invited speaker),
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+ − 137 <A HREF="http://www.cis.upenn.edu/~bcpierce/wmm/">WMM'10</A> (invited speaker),
+ − 138 <A HREF="http://isabelle.in.tum.de/nominal/activities/idw10/idw.html">IDW'10</A> (co-organiser),
+ − 139 <A HREF="http://formes.asia/cpp">CPP'11</A> (member of PC),
+ − 140 <A HREF="http://www.rdp2011.uns.ac.rs/rta/">RTA'11</A> (member of PC),
+ − 141 <A HREF="http://lfmtp11.cs.umn.edu">LFMTP'11</A> (member of PC)
+ − 142 <BR>
+ − 143
+ − 144 </TD>
+ − 145 </TR>
+ − 146
+ − 147 <TR>
+ − 148 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 149 <B>Nominal Isabelle</B>
+ − 150 I currently work on Nominal
+ − 151 <A HREF="http://isabelle.in.tum.de">Isabelle</A>. This is joint work with
+ − 152 <A HREF="http://wwwbroy.in.tum.de/~berghofe/">Dr Stefan Berghofer</A>,
+ − 153 <A HREF="http://www4.in.tum.de/~wenzelm/">Dr Markus Wenzel</A>,
+ − 154 <A HREF="http://www4.in.tum.de/~kaliszyk/">Dr Cezary Kaliszyk</A> and
+ − 155 the Isabelle-team in Munich.
+ − 156 Many of the theoretical ideas originate from the nominal logic project - a wonderful project headed
+ − 157 by <A HREF="http://www.cl.cam.ac.uk/~amp12/">Prof. Andrew Pitts</A>.
+ − 158 The aim of my work is to make formal reasoning involving binders as simple as
+ − 159 on paper and the hope is to lure
+ − 160 <A HREF="http://alliance.seas.upenn.edu/~plclub/cgi-bin/poplmark/index.php?title=The_POPLmark_Challenge#Vision">masses</A> to automated
+ − 161 theorem proving. My funding for this work was provided in 2004 and 2005 by a research
+ − 162 fellowship from the
+ − 163 <A HREF="http://en.wikipedia.org/wiki/Alexander_von_Humboldt">Alexander-von-Humboldt</A>
+ − 164 <A HREF="http://www.humboldt-foundation.de/web/home.html">foundation</A>. During this time I was a visitor in the group of
+ − 165 <A HREF="http://www.mathematik.uni-muenchen.de/~schwicht/">Prof. Helmut Schwichtenberg</A>.
+ − 166 Since 2006 this work is supported by an
+ − 167 <A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A>
+ − 168 <A HREF="http://www.dfg.de/en/research_funding/programmes/individual/emmy_noether/in_brief/index.html">fellowship</A>.
+ − 169 There is a <A HREF="http://isabelle.in.tum.de/nominal/">webpage</A> and a
+ − 170 <A HREF="https://mailmanbroy.informatik.tu-muenchen.de/mailman/listinfo/nominal-isabelle">mailing list</A>
+ − 171 about Nominal Isabelle. It also includes a list of projects that use Nominal Isabelle.
+ − 172 Users of Nominal Isabelle had their papers appearing at LICS, POPL, FOSSACS, SOS, TPHOLs and CPP.
+ − 173 </TD>
+ − 174 </TR>
+ − 175
+ − 176 <TR>
+ − 177 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 178 <B>Myhill-Nerode and Regular Expressions</B>
+ − 179 Out of frustration of having to teach inductions in theorem provers using worn-out examples like
+ − 180 fib and even/odd, we implemented a large part of regular language theory in Isabelle/HOL.
+ − 181 This <A HREF="http://afp.sourceforge.net/devel-entries/Myhill-Nerode.shtml">implementation</A>
+ − 182 gives rise to much more interesting examples, as shown
+ − 183 <A HREF="http://www.cs.cmu.edu/~rwh/papers/regexp/jfp.ps">here</A> and
+ − 184 <A HREF="http://ropas.snu.ac.kr/~kwang/paper/06-jfp-yi.pdf">here</A>. It turns out that
+ − 185 formalisations of automata theory are a huge
+ − 186 <A HREF="https://lists.cam.ac.uk/pipermail/cl-isabelle-users/2005-September/msg00012.html">pain</A>
+ − 187 in theorem provers, especially in those that are HOL-based.
+ − 188 We therefore went against the
+ − 189 <A HREF="http://books.google.com/books?id=8lKyxS8_CNoC&pg=PA14&source=gbs_toc_r&cad=4#v=onepage&q&f=false">mainstream</A>
+ − 190 and used in our formalisation regular expressions exclusively,
+ − 191 because they are much more convenient for formal reasoning. The results we
+ − 192 formalised include: the Myhill-Nerode theorem, the closure of regular languages
+ − 193 under complementation, finiteness of derivatives of regular expressions and a surprising
+ − 194 result about Subseq, which according to
+ − 195 this
+ − 196 <A HREF="http://blog.computationalcomplexity.org/2006/01/theorem-that-should-be-better-known.html">blog</A>
+ − 197 should be better known. This is joint work with Prof. Xingyuan
+ − 198 Zhang and his student Chunhan Wu from the
+ − 199 <A HREF="http://www.ust.com.cn/">PLA University of Science and Technology</A> in Nanjing.
+ − 200 My funding for this work came from the
+ − 201 <A HREF="http://www.sinogermanscience.org.cn/">Chinese-German Research Centre</A>.
+ − 202 </TD>
+ − 203 </TR>
+ − 204
+ − 205 <TR>
+ − 206 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 207 <B>Nominal Unification and Alpha-Prolog</B>
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+ − 208 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Unification">Nominal unification</A> is one outcome of
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+ − 209 my involvement in the nominal logic project in Cambridge. Another is the logic programming language
+ − 210 alpha-Prolog (joint work with <A HREF="http://homepages.inf.ed.ac.uk/jcheney/">Dr James Cheney</A>),
+ − 211 which uses nominal unification - click for details
+ − 212 <A HREF="http://homepages.inf.ed.ac.uk/jcheney/programs/aprolog/">here</A>.
+ − 213 The nominal unification algorithm has been
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+ − 214 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Unification">formally verified</A> in Isabelle. This
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+ − 215 was possible since this unification algorithm is formulated in a simple first-order language
+ − 216 (unlike other algorithms for higher-order unification).
+ − 217 <A HREF="http://www.cs.indiana.edu/~dfried/">Prof. Daniel Friedman</A> and his group use nominal
+ − 218 unification in their alpha-Kanren system implemented in Scheme.
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+ − 219 <A HREF="http://www.inf.kcl.ac.uk/staff/maribel/">Prof. Maribel Fernandez</A> and her student
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+ − 220 improved the nominal unification algorithm to be quadratic.
+ − 221 My funding for this work was provided through a research fellowship from
+ − 222 <A HREF="http://www.corpus.cam.ac.uk">Corpus Christi College</A>, Cambridge.
+ − 223 </TD>
+ − 224 </TR>
+ − 225
+ − 226 <TR>
+ − 227 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 228 <B>Classical Logic</B>
+ − 229 I was Ph.D. student in the University of Cambridge
+ − 230 <A HREF="http://www.cl.cam.ac.uk">Computer Laboratory</A>
+ − 231 and for three years
+ − 232 called Gonville and Caius College my home. I was very lucky to have
+ − 233 <A HREF="http://research.microsoft.com/~gmb/">Dr Gavin Bierman</A>
+ − 234 as supervisor. My research in Cambridge was also very much influenced by
+ − 235 <A HREF="http://www.dpmms.cam.ac.uk/~martin/">Prof. Martin Hyland</A>.
+ − 236 Some details on my thesis "Classical Logic and Computation" are
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+ − 237 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/PhD/index.html">elsewhere</A>, including
+ − 238 a <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Cut/cutapplet.html">Java Applet</A> that
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+ − 239 'visualises' some of the results from the thesis. I completed the writing of
+ − 240 the thesis in <A HREF="http://iml.univ-mrs.fr/ldp/">Marseille</A> in the group of
+ − 241 <A HREF="http://iml.univ-mrs.fr/~girard/">Prof. Jean-Yves Girard</A>. My study in
+ − 242 Cambridge was funded by two <A HREF="http://www.daad.de/index.html">scholarships</a>
+ − 243 from the German government; my year in Marseille by a TMR-fellowship from the EU.
+ − 244 My PhD was also one starting point for the EPSRC Project on the Semantics of Classical
+ − 245 Proofs. The strong normalisation result in the PhD has recently been used by
+ − 246 <A HREF="http://www.loria.fr/~ckirchne/hot.html">Prof. Claude Kirchner</A> and his
+ − 247 students to prove consistency for their superdeduction system lemuridae.
+ − 248 </TD>
+ − 249 </TR>
+ − 250
+ − 251
+ − 252
+ − 253 <TR>
+ − 254 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 255 <B>Forum</B>
+ − 256 I implemented Forum, a programming language based on classical linear logic,
+ − 257 as my M.Phil. thesis. This was joint work with
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+ − 258 <A HREF="http://www.inf.st-and.ac.uk/~rd/">Dr Roy Dyckhoff</A>.
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+ − 259 Details can be found
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+ − 260 <A HREF="http://www.inf.st-and.ac.uk/~rd/logic/nonmac/">here</A> and
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+ − 261 <A HREF="http://www.lix.polytechnique.fr/Labo/Dale.Miller/forum/">here</A>. During my
+ − 262 M.Phil study I spent one month in Philadelphia invited by
+ − 263 <A HREF="http://www.lix.polytechnique.fr/~dale/">Prof. Dale Miller</A>.
+ − 264 </TD>
+ − 265 </TR>
+ − 266
+ − 267 <TR>
+ − 268 <TD BGCOLOR="#FFFFFF" WIDTH="75%">
+ − 269 <B>G4ip</B> An implementation of G4ip using the imperative language Pizza can be found
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+ − 270 <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Prover/index.html">here</A>.
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+ − 271 <A HREF="http://pizzacompiler.sourceforge.net">Pizza</A> is a conservative
+ − 272 extension of Java and a precursor of Scala. The implementation illustrates the technique of success
+ − 273 continuations.
+ − 274 </TD>
+ − 275 </TR>
+ − 276
+ − 277
+ − 278 </TABLE>
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