Create a cross-reference (xref) to a file or web site in the Oxygen XML Editor
Use the xref element to create a hypertext link to remote systems, FTP sites, or local files outside the repository.
When you are cross-referencing files outside the repository, you may use either absolute or relative pathnames. However, you should keep in mind that setups vary in different machines. When you specify the path for your cross-referenced file, you should make sure that the path makes sense with regard to the machine (and the local network) where the files will be installed.