Class Pxp_reader.norm_system_id

class norm_system_id : resolver -> resolver

Normalizes URL's, and forwards the open request to the passed resolver. (Non-URL ID's are forwarded unchanged to the subresolver.)

Normalization includes:

• Relative URLs are made absolute. If this fails, the problematic relative URL will be rejected.
• .. and . and // in the middle of URLs are removed
• Escaping of reserved characters is normalized (percent encoding like %40)

Normalization is recommended for catalogs, e.g.  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.

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