whatever is in your public_html folder will show up at
http://myserver.com/filename.extI don't think a relative address like ../../filename will work from the device. If you have a php or other script running on your server, you might be able to reference things on the server like that, but not externally. A web page can generate an explicit reference from an relative url, but only because it knows the context.
Your xml needs an explicit path, unless you prepend a path to it when you are processing the xml on the device, but you still wind up with an explicit path.
The only way around using your domain name is if your server has a fixed ip address and then you can use that instead.
- Joel