GAP (Gpd) - Chapter 8: Development History

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8 Development History
8.1 Versions of the Package
8.2 What needs to be done next?

### 8 Development History

#### 8.1 Versions of the Package

The first version, GraphGpd 1.001, formed part of Emma Moore's thesis [Moo01] in December 2000, but was not made generally available.

Version 1.002 of GraphGpd was prepared to run under GAP 4.4 in January 2004; was submitted to the GAP 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 GAPDoc format. Variables `Star`, `Costar` and `CoveringGroup` were found to conflict with usage in other packages, and were renamed `VertexStar`, `VertexCostar` and `CoveringGroupOfGroupoid` respectively. Similarly, the `Vertices` and `Arcs` of an `FpWeightedDigraph` were changed from attributes to record components.

In the spring of 2006 the package was extensively rewritten and renamed Gpd. 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 `gpd_manual.tst`.

Version 1.05, of November 2008, was released when the website at Bangor changed.

Since then, the package has been rewritten again, introducing magmas with objects and their mappings. Functions to implement constructions contained in [AW10] have been added, but this is ongoing work.

Versions 1.09 to 1.15 were prepared for the anticipated release of GAP 4.5 in June 2012.

Gpd became an accepted GAP package in May 2015.

The latest version is 1.46 of 21st February 2017, for GAP 4.8.

(In this temporary version there have been a number of changes of function name, such as `IsDigraph` becoming `GpdIsDigraph`. This is in order to avoid conflicts with the new Digraphs package. Further changes will be made once the Digraphs package becomes part of the general GAP distribution.)

#### 8.2 What needs to be done next?

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.

GraphGpd attempted to implement the second case, while Gpd 1.01 and 1.03 considered only the first case, and Gpd 1.05 extended 1.03 to the second case.

The third case has not yet been considered for implementation, and there does not appear to be much need to do so.

Here are some other immediate requirements:

- more work on automorphism groups of groupoids;

- normal subgroupoids and quotient groupoids;

- more methods for morphisms of groupoids, particularly when the range is not connected;

- `ImageElm` and `ImagesSource` for the cases of groupoid morphisms not yet covered;

- `Enumerator` for `IsHomsetCosetsRep`;

- free groupoid on a graph;

- methods for `FreeProductWithAmalgamation` and `HnnEntension` for pc-groups;

- convert `GraphOfGroupsRewritingSystem` to the category `IsRewritingSystem`;

- in XMod, implement crossed modules over groupoids (a start has been made).

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