Is there any standard for storing metadata for user ordered files?

I plan to allow you to order files as you see fit (instead of requiring sort by name, date, etc) in WriteRoom’s file browser. For that to work I’ll need to store some metadata describing the sorting. I’m wondering if there’s some standard for this used by other apps.

If there’s no other suggestion I guess I’ll store the sorting for each directory in a hidden file named “.order” that contains each file name on a separate line.