Hi,
Yes V5R9 is the first Rx to manage standards using XML files. As I work very short time with R9 i migth not be of greqt help but amitkulk is right : look on the online help.
First have a look on the environement to be sure of the path for Standards files, then copy your xml file into xml.save and edit your xml file to make change.
restart CATIA.
It worked for me.
I made change for CATPart and CATDrawing... Changing Colors for Solid, surfaces, setting parameters for CATDrawing..
eric