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<TitlePage>
  <Title>
    XMod
  </Title>
  <Subtitle>
    Crossed Modules and Cat1-Groups
  </Subtitle>
  <Version>
    2.77
  </Version>
  <Author>
    Chris Wensley<Alt Only="LaTeX"><Br/></Alt>
<Address>
Dr. C.D. Wensley<Br/>
School of Computer Science and Electronic Engineering<Br/>
Bangor University<Br/>
Dean Street<Br/>
Bangor<Br/>
Gwynedd LL57 1UT<Br/>
UK<Br/>
</Address>
<Email>c.d.wensley@bangor.ac.uk</Email>
<Homepage>http://pages.bangor.ac.uk/~mas023/</Homepage>

  </Author>
  <Author>
    Murat Alp<Alt Only="LaTeX"><Br/></Alt>
<Address>
Prof. Dr. M. Alp<Br/>
Ömer Halisdemir University<Br/>
Art and Science Faculty<Br/>
Mathematics Department<Br/>
Nigde<Br/>
Turkey<Br/>
</Address>
<Email>muratalp@nigde.edu.tr</Email>

  </Author>
  <Author>
    Alper Odabas<Alt Only="LaTeX"><Br/></Alt>
<Address>
Dr. A. Odabas <Br/>
Osmangazi University <Br/>
Arts and Sciences Faculty <Br/>
Department of Mathematics and Computer Science <Br/>
Eskisehir <Br/>
Turkey<Br/>
</Address>
<Email>aodabas@ogu.edu.tr</Email>

  </Author>
  <Author>
    Enver Onder Uslu<Alt Only="LaTeX"><Br/></Alt>

  </Author>
  <Date>
    17 November 2019
  </Date>
  <Abstract>
    The &XMod; package provides functions for computation with
<List>
  <Item>
  finite crossed modules of groups and cat1-groups, 
  and morphisms of these structures; 
  </Item>
  <Item>
  finite pre-crossed modules, pre-cat1-groups,   and their Peiffer quotients;
  </Item>
  <Item>
  isoclinism classes of groups and crossed modules; 
  </Item>
  <Item>
  derivations of crossed modules and sections of cat1-groups; 
  </Item>
  <Item>
  crossed squares and their morphisms,   including the actor crossed square of a crossed module; 
  </Item>
  <Item>
  crossed modules of finite groupoids (experimental version). 
  </Item>
</List>
<P/>
&XMod; was originally implemented in 1996 using the &GAP;3 language, when the second author was studying for a Ph.D. <Cite Key='A1'/> in Bangor.
<P/>
In April 2002 the first and third parts were converted to &GAP;4, the pre-structures were added, and version 2.001 was released. 
The final two parts, covering derivations, sections and actors, were included in the January 2004 release 2.002 for &GAP; 4.4.
<P/>
In October 2015 functions for computing isoclinism classes of crossed modules, written by Alper Odaba&#x15f; and Enver Uslu, were added.
These are contained in Chapter <Ref Chap='chap-isclnc' />, and are described in detail in the paper <Cite Key='IOU1' />.
<P/>
Bug reports, suggestions and comments are, of course, welcome. Please submit an issue at <URL>https://github.com/gap-packages/xmod/issues/</URL> or send an email to the first author at <Email>c.d.wensley@bangor.ac.uk</Email>. 
<P/>

  </Abstract>
  <Copyright>
    &copyright; 1996-2019, Chris Wensley et al. <P/>
The &XMod; package is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

  </Copyright>
  <Acknowledgements>
    This documentation was prepared using the &GAPDoc; <Cite Key='GAPDoc'/> and &AutoDoc; <Cite Key='AutoDoc'/> packages.<P/>
The procedure used to produce new releases uses the package <Package>GitHubPagesForGAP</Package> <Cite Key='GitHubPagesForGAP' /> and the package <Package>ReleaseTools</Package>.<P/>
  </Acknowledgements>
  </TitlePage>