This function converts the absolute path name given by path into a relative path name if possible. If the file referenced by path is in or below the same directory as the document doc, a path name relative to the document directory is returned. If the file is located within a directory given by the ditapath Advanced Preference or set option, a path name relative to that directory is returned. Otherwise, the original input path name is returned.

If doc is zero or omitted, the current document is used.

This function is used by Arbortext Editor when storing file references in DITA documents.