1 Introduction
  
  This manual describes the IdRel (version 2.05) GAP package for computing the
  identities  among  relators  of a group presentation using rewriting, logged
  rewriting, monoid polynomials, module polynomials and Y-sequences.
  
  The  theoretical background for these computations is contained in Brown and
  Huebschumann  [BH82],  Brown  and  Razak  Salleh  [BS99]  and is surveyed in
  [Hey99].
  
  IdRel  is  primarily  designed  for  the  computation  of  a  minimal set of
  generators  for  the  module  of identities among relators. It also contains
  functions  which compute logged rewrite systems for group presentations (and
  complete  them  where possible), functions for operations involving elements
  of  monoid rings and functions for operations with elements of right modules
  over  monoid  rings.  The  Y-sequences  are  used  as  a  rewriting  way  of
  representing  elements  of  a free crossed module (products of conjugates of
  group  relators  and  inverse  relators). The package is written entirely in
  GAP4, and requires no compilation.
  
  The  package  is  loaded  into GAP with the LoadPackage command, and on-line
  help is available in the usual way.
  
  ---------------------------  Example  ----------------------------
    
    gap> LoadPackage( "idrel" ); 
    gap> ?idrel
    
  ------------------------------------------------------------------
  
  A  pdf  version of the IdRel manual is available in the doc directory of the
  home  directory  of  IdRel.  The information parameter InfoIdRel has default
  value  0.  When  raised to a higher value, additional information is printed
  out.  IdRel was originally developed in 1999 using GAP3, partially supported
  by  a  University of Wales Research Assistantship for the first author, Anne
  Heyworth.
  
  If  you  use  IdRel to solve a problem then please send a short email to the
  second  author,  to  whom bug reports, suggestions and other comments should
  also  be  sent.  You  may  reference  the  package  by mentioning [HW03] and
  [Hey99].
  
  The new version (2.05) was required in November 2008 because the Mathematics
  website  at  Bangor  moved to a different network, and the IdRel pages moved
  with it.