Administrative Template File (ADMX) Format
Beginning with Windows Vista and Windows 2000, Group Policy Object Editor and Group Policy Management Console can obtain registry-based policy settings from an XML-based administrative template file. The format is defined as a set of one language neutral file (.admx) and associated language resource files (.adml).
The syntax for .admx and .adml files is defined through the PolicyDefinitions schema and the CommentDefinitions schema
For more information about the schema element definitions, see the following: