  
  [1X5. Development History[0X
  
  
  [1X5.1 Versions of the Package[0X
  
  The  first  version,  [5XGraphGpd[0X  1.001,  formed  part  of Emma Moore's thesis
  [Moo01] in December 2000, but was not made generally available.
  
  Version 1.002 of [5XGraphGpd[0X was prepared to run under [5XGAP[0X 4.4 in January 2004;
  was  submitted  to  the [5XGAP[0X council to be considered as an accepted package;
  but suggestions from the referee were not followed up.
  
  In  April  2006  the  manual was converted to [5XGAPDoc[0X format. Variables [10XStar[0X,
  [10XCostar[0X  and  [10XCoveringGroup[0X  were  found  to  conflict  with  usage  in other
  packages,     and     were     renamed    [10XVertexStar[0X,    [10XVertexCostar[0X    and
  [10XCoveringGroupOfGroupoid[0X respectively. Similarly, the [10XVertices[0X and [10XArcs[0X of an
  [10XFpWeightedDigraph[0X were changed from attributes to record components.
  
  In the spring of 2006 the package was extensively rewritten and renamed [5XGpd[0X.
  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 [11Xgpd_manual.tst[0X.
  
  
  [1X5.2 What needs to be done next?[0X
  
  Computationally, there are three types of connected groupoid:
  
  --    those with identical object groups,
  
  --    those with object groups conjugate in some supergroup,
  
  --    those with object groups which are simply isomorphic.
  
  [5XGraphGpd[0X  attempted  to  implement  the second case, while [5XGpd[0X 1.01 and 1.03
  considered  only the first case, and [5XGpd[0X 1.04 will extend 1.03 to the second
  case. Here are some other immediate requirements:
  
  --    Automorphism group of a groupoid.
  
  --    normal subgroupoids and quotient groupoids;
  
  --    more  methods  for morphisms of groupoids, particularly when the range
        is not connected;
  
  --    [10XImageElm[0X  and [10XImagesSource[0X for the cases of groupoid morphisms not yet
        covered;
  
  --    [10XEnumerator[0X for [10XIsHomsetCosetsRep[0X;
  
  --    free groupoid on a graph;
  
  --    methods   for   [10XFreeProductWithAmalgamation[0X   and   [10XHnnEntension[0X   for
        pc-groups;
  
  --    convert      [10XGraphOfGroupsRewritingSystem[0X      to     the     category
        [10XIsRewritingSystem[0X;
  
  --    in [5XXMod[0X, implement crossed modules over groupoids.
  
