| author | Christian Urban <urbanc@in.tum.de> |
| Thu, 20 Sep 2018 11:00:47 +0100 | |
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ROWSPAN="9"> |
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<B>Links</B><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/index.html">Home</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/publications.html">Publications</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/teaching.html">Teaching</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/travelling.html">Recent Talks</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/">Nominal Isabelle</A> |
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<BR> |
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<BR> |
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<B>Handy Information</B><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/logic.html">People in Logic</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/programming.html">Programming Languages</A><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/misc.html">Miscellaneous</A> |
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<BR><BR> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/"> |
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<IMG SRC="nominal-logo.gif" ALT="" style="border-width: 0px;" align="left"></A> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Cookbook/"> |
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<IMG SRC="Cookbook/logo-documentation.gif" ALT="" style="border-width: 0px;" align="left"></A> |
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<A NAME="Home"></A> |
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<TABLE> |
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<H1>Christian Urban</H1> |
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<B>E-mail</B> |
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christian.urban <I>at</I> kcl ac uk<BR> |
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<BR> |
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<B>Address</B> |
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<A HREF="http://www.kcl.ac.uk/nms/depts/informatics/">Department of Informatics</A>, |
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<A HREF="http://www.kcl.ac.uk">King's College London</A>, |
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Bush House, 30 Aldwych, London WC2B 4BG, UK. My office is 7.07 on the 7th floor, North Wing, of the Bush House. |
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<BR> |
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</TD> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/picture-small.jpg"><IMG ALT="" SRC="picture-small.jpg" align="top"></A> |
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<p> |
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<IMG SRC="new.gif" ALT="" style="" align="left"><A HREF="https://nms.kcl.ac.uk/christian.urban/Cookbook" target="_top">Isabelle Programming Tutorial</A> (draft of a 200-page tutorial on Isabelle programming)<BR><BR> |
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<B>Current Position</B> |
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Since 2011 I have been a lecturer in the Department of Informatics at King's College London. |
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This is similar to a position of an assistant professor in other places. In 2011, |
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I was also offered a lectureship |
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<A HREF="http://www.it.uu.se/" TITLE="Uppsala">here</A>, an associate professorship |
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<A HREF="http://en.itu.dk/" TITLE="ITU, Copenhagen">here</A>, |
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and full professorships |
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<A HREF="https://en.wikipedia.org/wiki/University_of_Science_and_Technology_of_China" TITLE="IAS, Suzhou">here</A> and |
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<A HREF="https://en.wikipedia.org/wiki/East_China_Normal_University" TITLE="Shanghai">here</A>. |
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I thank all people involved for their efforts. |
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<P> |
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<B>Past Positions</B> |
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In April 2006, I was awarded an <A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A> |
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<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 |
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September 2011. |
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Between September 2008 and February 2009, I was an invited research scientist in |
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the <A HREF="http://www.cs.princeton.edu/">Department of Computer Science</A> in Princeton. |
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In 2004/05 I was an Alexander-von-Humboldt fellow in Munich and |
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from 2000 until 2004 I was awarded a Research Fellowship in Cambridge. Before that |
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I did my PhD in Cambridge funded by two scholarships from the German Academic Exchange |
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Service (<A HREF="http://www.daad.de/index.html">DAAD</A>). |
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<P> |
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<B>Skolem Award 2015</B> Together with |
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<A HREF="http://www.pps.univ-paris-diderot.fr/~tasson/">Christine Tasson</A>, I was awarded a |
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<A HREF="http://cadeinc.org/Skolem-Award">Thoralf Skolem Award</A>, a ten-year |
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test-of-time award from CADE. This was for our |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Publications/nom-cade-05.ps">paper</A> |
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on Nominal Techniques in Isabelle/HOL from 2005. The Skolem Award award was given also |
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to Nicolaas de Bruijn, Zohar Manna and |
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Nachum Derschowitz, amongst others. |
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<P> |
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<B>Research Interests</B> theorem provers, verification, programming languages, compilers, |
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algorithms, security, proof theory, type systems, concurrency, lambda calculus, unification, |
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regular expressions, computability, complexity, functional and logic programming. |
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<B>Teaching</B> I usually enjoy teaching. At King's my students nominated me for the Teaching |
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Excellence Award in |
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2012, 2015, 2016 and 2017, and for the best MSc Project supervisor in 2015. |
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In 2014 I received both prizes for Best UG Project Supervisor and for Best |
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MSc Project Supervisor in the <A HREF="http://www.kcl.ac.uk/nms/index.aspx">NMS Faculty</A>.<P> |
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<B>Conferences</B> |
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UNIF'06 (member of PC), |
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<A HREF="http://www.cs.mcgill.ca/~bpientka/lfmtp07">LFMTP'07</A> (member of PC), |
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LFMTP'08 (PC co-chair), |
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<A HREF="http://www.cis.upenn.edu/~sweirich/wmm/">WMM'08</A> (member of PC), |
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<A HREF="http://www.mat.ufmg.br/lsfa2008/">LSFA'08</A> (invited speaker), |
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<A HREF="http://www.inf.kcl.ac.uk/staff/maribel/TAASN.html">TAASN'09</A> (member of PC), |
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<A HREF="http://lsfa09.cic.unb.br/">LSFA'09</A> (member of PC), |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/activities/tphols09/idw.html">IDW'09</A> (organiser), |
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<A HREF="http://www.seas.upenn.edu/~sweirich/wmm/wmm09.html">WMM'09</A> (PC chair), |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/activities/tphols09/">TPHOLs'09</A> (PC co-chair), |
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<A HREF="http://dream.inf.ed.ac.uk/events/automatheo-2010/">Automatheo'10</A> (member of PC), |
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<A HREF="http://www.floc-conference.org/">ITP'10</A> (member of PC), |
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UNIF'10 (invited speaker), |
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<A HREF="http://www.cis.upenn.edu/~bcpierce/wmm/">WMM'10</A> (invited speaker), |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/activities/idw10/idw.html">IDW'10</A> (co-organiser), |
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CPP'11 (member of PC), |
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<A HREF="http://www.rdp2011.uns.ac.rs/rta/">RTA'11</A> (member of PC), |
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<A HREF="http://lfmtp11.cs.umn.edu">LFMTP'11</A> (member of PC), |
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<A HREF="http://www.cs.uwyo.edu/~ruben/itp-2014">ITP'14</A> (member of PC), |
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<A HREF="http://www.cicm-conference.org/2015/cicm.php?event=mkm">MKM'15</A> (member of PC), |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/itp-2015/">ITP'15</A> (PC co-chair), |
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<A HREF="https://itp2016.inria.fr">ITP'16</A> (member of PC) |
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<A HREF="http://lsfa.cic.unb.br">LSFA'17</A> (member of PC) |
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<A HREF="http://itp2017.cic.unb.br">ITP'17</A> (member of PC) |
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<P> |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/itp-2015/">ITP'15</A> took place in Nanjing organised |
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by Xingyuan Zhang and me<BR> |
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<p> |
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<B>Current PhDs</B> Chengsong Tan, Reham Alhejaili<BR> |
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<B>Former PhD</B> Fahad Ausaf (works at ARM in the VHDL compiler team)<BR> |
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<B>Former RAs</B> Chunhan Wu, <A HREF="http://cl-informatik.uibk.ac.at/users/cek/">Cezary Kaliszyk</A>, |
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<A HREF="http://dpt-info.u-strasbg.fr/~narboux/">Julien Narboux</A><p> |
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If I am not teaching or not doing research, I am sometimes in the lavender |
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<A HREF="https://nms.kcl.ac.uk/christian.urban/family.jpg">fields</A> of London. |
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</TD> |
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<B>Nominal Isabelle</B> |
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I currently work on Nominal |
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<A HREF="http://isabelle.in.tum.de">Isabelle</A> 2. This is joint work with |
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<A HREF="http://wwwbroy.in.tum.de/~berghofe/">Dr Stefan Berghofer</A>, |
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<A HREF="http://sketis.net/">Dr Markus Wenzel</A>, |
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<A HREF="http://cl-informatik.uibk.ac.at/users/cek/">Dr Cezary Kaliszyk</A>, |
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<A HREF="http://user.it.uu.se/~tjawe125/">Dr Tjark Weber</A> and |
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the Isabelle-team in Munich. |
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Many of the theoretical ideas originate from the nominal logic project - a wonderful project headed |
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by <A HREF="http://www.cl.cam.ac.uk/~amp12/">Prof. Andrew Pitts</A>. |
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The aim of my work is to make formal reasoning involving binders as simple as |
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on paper and the hope is to lure |
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<A HREF="http://alliance.seas.upenn.edu/~plclub/cgi-bin/poplmark/index.php?title=The_POPLmark_Challenge#Vision">masses</A> to automated |
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theorem proving. My funding for this work was provided in 2004 and 2005 by a research |
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fellowship from the |
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<A HREF="http://en.wikipedia.org/wiki/Alexander_von_Humboldt">Alexander-von-Humboldt</A> |
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<A HREF="http://www.humboldt-foundation.de/web/home.html">foundation</A>. During this time I was a visitor in the group of |
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<A HREF="http://www.mathematik.uni-muenchen.de/~schwicht/">Prof. Helmut Schwichtenberg</A>. |
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Since 2006 this work is supported by an |
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<A HREF="http://en.wikipedia.org/wiki/Emmy_Noether">Emmy-Noether</A> |
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<A HREF="http://www.dfg.de/en/research_funding/programmes/individual/emmy_noether/in_brief/index.html">fellowship</A>. |
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There is a <A HREF="https://nms.kcl.ac.uk/christian.urban/Nominal/">webpage</A> and a |
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<A HREF="https://mailmanbroy.informatik.tu-muenchen.de/mailman/listinfo/nominal-isabelle">mailing list</A> |
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about Nominal Isabelle. It also includes a list of projects that use Nominal Isabelle. |
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Users of Nominal Isabelle had their papers appearing at LICS, POPL, FOSSACS, SOS, TPHOLs, CPP, SEFM, |
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the Haskell Symposium and |
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in the Journal of Automated Reasoning. |
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<B>Myhill-Nerode and Regular Expressions</B> |
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Out of frustration of having to teach reasoning in theorem provers with worn-out examples like |
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fib and even/odd, we implemented a large part of regular language theory in Isabelle/HOL. |
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This <A HREF="http://afp.sourceforge.net/devel-entries/Myhill-Nerode.shtml">implementation</A> |
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gives rise to much more interesting examples, as shown |
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<A HREF="http://www.cs.cmu.edu/~rwh/papers/regexp/jfp.pdf">here</A> and |
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<A HREF="http://ropas.snu.ac.kr/~kwang/paper/06-jfp-yi.pdf">here</A>. It turns out that |
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formalisations of automata theory are a huge |
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<A HREF="https://lists.cam.ac.uk/pipermail/cl-isabelle-users/2005-September/msg00012.html">pain</A> |
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in theorem provers, especially in those that are based on HOL. |
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We therefore went against the |
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<A HREF="http://www.cs.cornell.edu/~kozen/papers/papers_by_year.htm#K97a">mainstream</A> |
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and used in our formalisation regular expressions exclusively, |
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because they are much more convenient for formal reasoning. The results we |
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formalised include: the Myhill-Nerode theorem, the closure of regular languages |
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under complementation, finiteness of derivatives of regular expressions and a surprising |
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result about Subseq, which according to |
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this |
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<A HREF="http://blog.computationalcomplexity.org/2006/01/theorem-that-should-be-better-known.html">blog</A> |
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should be better known. We also answered a |
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<A HREF="http://blog.computationalcomplexity.org/2013/02/proving-dfa-langs-closed-under-concat.html">question</A> from the same blog about |
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"proving Reg-exp-langs [being] closed under complementation without using equiv to DFA's"....yes we can! |
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This is joint work with Prof. Xingyuan |
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Zhang and his student Chunhan Wu from the |
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<A HREF="http://www.ust.com.cn/">PLA University of Science and Technology</A> in Nanjing. |
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My funding for this work came from the |
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<A HREF="http://www.sinogermanscience.org.cn/">Chinese-German Research Centre</A>. |
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</TD> |
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<B>Priority Inheritance</B> |
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In real-time operating systems with processes, resource locking and |
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priority scheduling, one faces the problem of indefinite |
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<A HREF="http://en.wikipedia.org/wiki/Priority_inversion">priority inversion</A> (processes |
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with lower priority block processes with higher priority). If you do not prevent this problem, |
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then processes can behave quite erratically, as <A HREF="http://www.nasa.gov">NASA</A> found out the |
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<A HREF="http://catless.ncl.ac.uk/Risks/19.54.html#subj6">hard</A> way with their |
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<A HREF="http://www.nasa.gov/mission_pages/mars-pathfinder/index.html">Mars Pathfinder mission</A>. |
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The priority inheritance protocol is a widely used scheduling algorithm that prevents |
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priority inversion. However, the <A HREF="http://dx.doi.org/10.1109/12.57058">original paper</A> |
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describing this algorithm contains an incorrect algorithm and a bogus correctness proof |
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(this seems to be the only "proof" about priority inheritance in the literature). |
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We formalised the priority inheritance protocol, including a generalisation |
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of the original work. |
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using the inductive method we learned from |
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<A HREF="https://www.cl.cam.ac.uk/~lp15/">Prof. Larry Paulson</A>. |
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While the problem with the original algorithm was already known, the incorrect |
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specification seems to be still in use |
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<A HREF="http://mcs.une.edu.au/%7Eiam/Data/threads/node15.html">here</A> |
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<A HREF="http://ems2.be/Portals/6/course_docs/OS_pathfinder_failure.ppt"> |
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|
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This is joint work with Prof. Xingyuan Zhang and his student Chunhan Wu from the |
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<A HREF="http://www.ust.com.cn/">PLA University of Science and Technology</A> in Nanjing. |
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</TD> |
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</TR> |
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--> |
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<TR> |
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<TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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<B>Nominal Unification and Alpha-Prolog</B> |
|
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Unification">Nominal unification</A> is one outcome of |
| 2 | 295 |
my involvement in the nominal logic project in Cambridge. Another is the logic programming language |
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alpha-Prolog (joint work with <A HREF="http://homepages.inf.ed.ac.uk/jcheney/">Dr James Cheney</A>), |
|
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which uses nominal unification - click for details |
|
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<A HREF="http://homepages.inf.ed.ac.uk/jcheney/programs/aprolog/">here</A>. |
|
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The nominal unification algorithm has been |
|
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<A HREF="https://nms.kcl.ac.uk/christian.urban/Unification">formally verified</A> in Isabelle. This |
| 2 | 301 |
was possible since this unification algorithm is formulated in a simple first-order language |
302 |
(unlike other algorithms for higher-order unification). |
|
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<A HREF="https://nms.kcl.ac.uk/maribel.fernandez/">Prof. Maribel Fernandez</A> and her student |
| 2 | 304 |
improved the nominal unification algorithm to be quadratic. |
|
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Christian Urban <christian dot urban at kcl dot ac dot uk>
parents:
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<A HREF="http://www.cs.indiana.edu/~dfried/">Prof. Daniel Friedman</A> and his group use nominal |
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parents:
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unification in their alpha-Kanren system implemented in Scheme. This work has also found its |
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way into <A HREF="http://clojure.org">Clojure</A> as the <A HREF="https://github.com/clojure/core.logic/wiki/core.logic.nominal">core.logic.nominal</A> package. |
| 2 | 308 |
My funding for this work was provided through a research fellowship from |
309 |
<A HREF="http://www.corpus.cam.ac.uk">Corpus Christi College</A>, Cambridge. |
|
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</TD> |
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</TR> |
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<TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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<B>Classical Logic</B> |
|
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I was Ph.D. student in the University of Cambridge |
|
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<A HREF="http://www.cl.cam.ac.uk">Computer Laboratory</A> |
|
318 |
and for three years |
|
319 |
called Gonville and Caius College my home. I was very lucky to have |
|
| 362 | 320 |
<A HREF="https://labs.oracle.com/pls/apex/f?p=labs:bio:0:2044">Dr Gavin Bierman</A> |
| 2 | 321 |
as supervisor. My research in Cambridge was also very much influenced by |
322 |
<A HREF="http://www.dpmms.cam.ac.uk/~martin/">Prof. Martin Hyland</A>. |
|
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Some details on my thesis "Classical Logic and Computation" are |
|
| 519 | 324 |
<A HREF="https://nms.kcl.ac.uk/christian.urban/PhD/index.html">elsewhere</A>, including |
325 |
a <A HREF="https://nms.kcl.ac.uk/christian.urban/Cut/cutapplet.html">Java Applet</A> that |
|
| 2 | 326 |
'visualises' some of the results from the thesis. I completed the writing of |
327 |
the thesis in <A HREF="http://iml.univ-mrs.fr/ldp/">Marseille</A> in the group of |
|
328 |
<A HREF="http://iml.univ-mrs.fr/~girard/">Prof. Jean-Yves Girard</A>. My study in |
|
329 |
Cambridge was funded by two <A HREF="http://www.daad.de/index.html">scholarships</a> |
|
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from the German government; my year in Marseille by a TMR-fellowship from the EU. |
|
331 |
My PhD was also one starting point for the EPSRC Project on the Semantics of Classical |
|
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Proofs. The strong normalisation result in the PhD has been used in 2007 by |
| 2 | 333 |
<A HREF="http://www.loria.fr/~ckirchne/hot.html">Prof. Claude Kirchner</A> and his |
| 66 | 334 |
students for proving consistency of their superdeduction system lemuridae. |
| 2 | 335 |
</TD> |
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<TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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<B>Forum</B> |
|
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I implemented Forum, a programming language based on classical linear logic, |
|
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as my M.Phil. thesis. This was joint work with |
|
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<A HREF="https://rd.host.cs.st-andrews.ac.uk">Dr Roy Dyckhoff</A>. |
| 2 | 346 |
Details can be found |
| 469 | 347 |
<A HREF="https://rd.host.cs.st-andrews.ac.uk/logic/nonmac/">here</A> and |
| 2 | 348 |
<A HREF="http://www.lix.polytechnique.fr/Labo/Dale.Miller/forum/">here</A>. During my |
349 |
M.Phil study I spent one month in Philadelphia invited by |
|
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<A HREF="http://www.lix.polytechnique.fr/~dale/">Prof. Dale Miller</A>. |
|
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</TD> |
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</TR> |
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<TR> |
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<TD BGCOLOR="#FFFFFF" WIDTH="75%"> |
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<B>G4ip</B> An implementation of G4ip using the imperative language Pizza can be found |
|
| 519 | 357 |
<A HREF="https://nms.kcl.ac.uk/christian.urban/Prover/index.html">here</A>. |
| 67 | 358 |
<A HREF="http://pizzacompiler.sourceforge.net">Pizza</A>, written around 1996, is a conservative |
| 69 | 359 |
extension of Java and a precursor of Scala. My implementation illustrates the technique of |
| 70 | 360 |
success continuations in proof search. |
| 2 | 361 |
</TD> |
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</TR> |
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</TABLE> |
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<P> |
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Time-stamp: <- 2017-09-26 19:52:51 by Christian Urban> |
| 503 | 368 |
<a href="https://validator.w3.org/check/referer">[Validate this page.]</a> |
| 2 | 369 |
</BODY> |
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</HTML> |