As was already mentioned, even if your site will be isolated from others, you should still try to register a unique global prefix.
If your site will be isolated from other sites you will have to set up a replica of the global root. This directory must be reachable with the name ``#'' from your site's master list of virtual systems. To create a replica of the global root, create a directory and add nested subdirectories corresponding to each component of your sites global prefix. The last entry should be a link to your site's master list of virtual systems.