may be given in abbreviated form, where parts of the two URIs are the
   same. This allows objects within a group to refer to each other




 
RFC 1630                      URIs in WWW                      June 1994


   without requiring the space for a complete reference, and it
   incidentally allows the group of objects to be moved without changing
   any references.  It must be emphasized that when a reference is
   passed in anything other than a well controlled context, the full
   form must always be used.

   In the World-Wide Web applications, the context URI is that of the
   document or object containing a reference. In this case partial URIs
   can be generated in virtual objects or stored in real objects,
   without the need for dramatic change if the higher-order parts of a
   hierarchical naming system are modified.  Apart from terseness, this
   gives greater robustness to practical systems, by enabling
   information hiding between system components.

   The partial form relies on a property of the URI syntax that certain
   characters ("/") and certain path elements ("..", ".") have a
   significance reserved for representing a hierarchical space, and must
   be recognized as such by both clients and servers.

   A partial form can be distinguished from an absolute form in that the
   latter must have a colon and that colon must occur before any slash
   characters. Systems not requiring partial forms should not use any
   unencoded slashes in their naming schemes.  If they do, absolute URIs
   will still work, but confusion may result. (See note on Gopher
   below.)

   The rules for the use of a partial name relative to the URI of the
   context are:

      If the scheme parts are different, the whole absolute URI must
      be given.  Otherwise, the scheme is omitted, and:

      If the partial URI starts with a non-zero number of consecutive
      slashes, then everything from the context URI up to (but not
      including) the first occurrence of exactly the same number of
      consecutive slashes which has no greater number of consecutive
      slashes anywhere to the right of it is taken to be the same and
      so prepended to the partial URL to form the full URL. Otherwise:

      The last part of the path of the context URI (anything following
      the rightmost slash) is removed, and the given partial URI
      appended in its place, and then:

      Within the result, all occurrences of "xxx/../" or "/." are
      recursively removed, where xxx, ".." and "." are complete path
      elements.






 
RFC 1630                      URIs in WWW                      June 1994


      Note: Trailing slashes

   If a path of the context locator ends in slash, partial URIs are
   treated differently to the URI with the same path but without a
   trailing slash. The trailing slash indicates a void segment of the
   path.

      Note: Gopher

   The gopher system does not have the concept of relative URIs, and the
   gopher community currently allows / as data characters in gopher URIs
   without escaping them to %2F.  Relative forms may not in general be
   used for documents served by gopher servers.  If they are used, then
   WWW software assumes, normally correctly, that in fact they do have
   hierarchical significance despite the specifications. The use of HTTP
   rather than gopher protocol is however recommended.

   Examples

   In the context of URI

                        magic://a/b/c//d/e/f

   the partial URIs would expand as follows:

   g                       magic://a/b/c//d/e/g

   /g                      magic://a/g

   //g                     magic://g

   ../g                    magic://a/b/c//d/g

   g:h                     g:h