A codebook of variables in the file is available as a PDF - last updated 10 October 2006.
For an online version of the codebook see the variable list.
The output glossary for the 2001 Individual SAR is available here. It contains detailed information on the creation of the SAR from the ONS Census Output database. Variables names here reflect ONS naming conventions, and may not be identical to that in the SAR documentation.
This is available from ONS: http://www.statistics.gov.uk/census2001/outputclassifications.asp
These files are the SARs documentation in XML DDI format, as used internally in our Nesstar server. Most users will not find these useful and would be better looking at the documentation or dataset pages rather than this raw metadata.