class norm_system_id :Normalizes URL's, and forwards the open request to the passed resolver. (Non-URL ID's are forwarded unchanged to the subresolver.)resolver ->resolver
Normalization includes:
.. and . and // in the middle of URLs are removed  new norm_system_id
   (new lookup_system_id_as_file
      [ "http://h/p1", ...;
        "http://h/p2", ...;
      ])
 
 First, the catalog now even works if the URL is written in an
 unsual way, e.g. http://h/p1/../p2, or http://h/p%31. 
 Second, relative URLs can be used. For instance, the document
 referred to as http://h/p1 can now refer to the other document
 as p2.