RDML File Compression and File extensions

The xml file containing the RDML compliant data should be stored in a
file named rdml_data.xml. This file should be compressed using pkzip
compatible compression into an archive. The archive can have any name,
but instead of having the extension .zip it should have the extension
.rdml (preferably) or .rdm.
Archives ending in .rdml or .rdm should only contain one file, the file
rdml_data.xml.
Software should be able to read compressed .rdml or .rdm files as well
as uncompressed .xml files.