+A pathname is a designator for a filename: the filename is computed
+using the same mechanism as the implementation would use to map
+pathnames to OS filenames internally.
+
+In an implementation that supports pathnames to files on other hosts,
+using mechanisms not available to the underlying OS (for example,
+using an FTP or HTTP client in the Lisp implementation), the effect
+of supplying this interface with a pathname to such a file is undefined.
+