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<div class="ChapSects"><a href="chap7.html#X810C43BC7F63C4B4">7 <span class="Heading">Development History</span></a>
<div class="ContSect"><span class="nocss"> </span><a href="chap7.html#X8192EA4C7B7CC5CD">7.1 <span class="Heading">Versions of the Package</span></a>
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<div class="ContSect"><span class="nocss"> </span><a href="chap7.html#X82148FB77CC3CCC0">7.2 <span class="Heading">What needs to be done next?</span></a>
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<h3>7 <span class="Heading">Development History</span></h3>
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<h4>7.1 <span class="Heading">Versions of the Package</span></h4>
<p>The first version, <strong class="pkg">GraphGpd</strong> 1.001, formed part of Emma Moore's thesis <a href="chapBib.html#biBemma-thesis">[Moo01]</a> in December 2000, but was not made generally available.</p>
<p>Version 1.002 of <strong class="pkg">GraphGpd</strong> was prepared to run under <strong class="pkg">GAP</strong> 4.4 in January 2004; was submitted to the <strong class="pkg">GAP</strong> council to be considered as an accepted package; but suggestions from the referee were not followed up.</p>
<p>In April 2006 the manual was converted to <strong class="pkg">GAPDoc</strong> format. Variables <code class="code">Star</code>, <code class="code">Costar</code> and <code class="code">CoveringGroup</code> were found to conflict with usage in other packages, and were renamed <code class="code">VertexStar</code>, <code class="code">VertexCostar</code> and <code class="code">CoveringGroupOfGroupoid</code> respectively. Similarly, the <code class="code">Vertices</code> and <code class="code">Arcs</code> of an <code class="code">FpWeightedDigraph</code> were changed from attributes to record components.</p>
<p>In the spring of 2006 the package was extensively rewritten and renamed <strong class="pkg">Gpd</strong>. Version 1.01 was submitted as a deposited package in June 2006. Version 1.03, of October 2007, fixed some file protections, and introduced the test file <code class="file">gpd_manual.tst</code>.</p>
<p>Version 1.05, of November 2008, was released because the website at Bangor changed.</p>
<p><em>A further extensive rewrite is in progress, introducing magmas with objects and their mappings, but many of the functions fail to work at present, and this manual is far from correct.</em></p>
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<h4>7.2 <span class="Heading">What needs to be done next?</span></h4>
<p>Computationally, there are three types of connected groupoid:</p>
<ul>
<li><p>those with identical object groups,</p>
</li>
<li><p>those with object groups conjugate in some supergroup,</p>
</li>
<li><p>those with object groups which are simply isomorphic.</p>
</li>
</ul>
<p><strong class="pkg">GraphGpd</strong> attempted to implement the second case, while <strong class="pkg">Gpd</strong> 1.01 and 1.03 considered only the first case, and <strong class="pkg">Gpd</strong> 1.05 extended 1.03 to the second case. Here are some other immediate requirements:</p>
<ul>
<li><p>Automorphism group of a groupoid.</p>
</li>
<li><p>normal subgroupoids and quotient groupoids;</p>
</li>
<li><p>more methods for morphisms of groupoids, particularly when the range is not connected;</p>
</li>
<li><p><code class="code">ImageElm</code> and <code class="code">ImagesSource</code> for the cases of groupoid morphisms not yet covered;</p>
</li>
<li><p><code class="code">Enumerator</code> for <code class="code">IsHomsetCosetsRep</code>;</p>
</li>
<li><p>free groupoid on a graph;</p>
</li>
<li><p>methods for <code class="code">FreeProductWithAmalgamation</code> and <code class="code">HnnEntension</code> for pc-groups;</p>
</li>
<li><p>convert <code class="code">GraphOfGroupsRewritingSystem</code> to the category <code class="code">IsRewritingSystem</code>;</p>
</li>
<li><p>in <strong class="pkg">XMod</strong>, implement crossed modules over groupoids.</p>
</li>
</ul>
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