can then be used in assembling a URI.  The reserved characters will
   vary from context to context, but will always be drawn from this set:

      reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" | "$" |
                 "," | "[" | "]"

   The last two characters were added by RFC 2732 [7].  In any
   particular context, a sub-set of these characters will be reserved;
   the other characters from this set MUST NOT be encoded when a string
   is URL-encoded in that context.  Other basic rules used to describe
   URI syntax are:

      hex        = digit | "A" | "B" | "C" | "D" | "E" | "F" | "a" | "b"
                   | "c" | "d" | "e" | "f"
      escaped    = "%" hex hex
      unreserved = alpha | digit | mark
      mark       = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"

3.  Invoking the Script

3.1.  Server Responsibilities

   The server acts as an application gateway.  It receives the request
   from the client, selects a CGI script to handle the request, converts
   the client request to a CGI request, executes the script and converts
   the CGI response into a response for the client.  When processing the
   client request, it is responsible for implementing any protocol or
   transport level authentication and security.  The server MAY also
   function in a 'non-transparent' manner, modifying the request or
   response in order to provide some additional service, such as media
   type transformation or protocol reduction.

   The server MUST perform translations and protocol conversions on the
   client request data required by this specification.  Furthermore, the
   server retains its responsibility to the client to conform to the
   relevant network protocol even if the CGI script fails to conform to
   this specification.

   If the server is applying authentication to the request, then it MUST
   NOT execute the script unless the request passes all defined access
   controls.









 
RFC 3875                    CGI Version 1.1                 October 2004


3.2.  Script Selection

   The server determines which CGI is script to be executed based on a
   generic-form URI supplied by the client.  This URI includes a
   hierarchical path with components separated by "/".  For any
   particular request, the server will identify all or a leading part of
   this path with an individual script, thus placing the script at a
   particular point in the path hierarchy.  The remainder of the path,
   if any, is a resource or sub-resource identifier to be interpreted by
   the script.

   Information about this split of the path is available to the script
   in the meta-variables, described below.  Support for non-hierarchical
   URI schemes is outside the scope of this specification.

3.3.  The Script-URI

   The mapping from client request URI to choice of script is defined by
   the particular server implementation and its configuration.  The
   server may allow the script to be identified with a set of several
   different URI path hierarchies, and therefore is permitted to replace
   the URI by other members of this set during processing and generation
   of the meta-variables.  The server

      1. MAY preserve the URI in the particular client request; or

      2. it MAY select a canonical URI from the set of possible values
         for each script; or

      3. it can implement any other selection of URI from the set.

   From the meta-variables thus generated, a URI, the 'Script-URI', can
   be constructed.  This MUST have the property that if the client had
   accessed this URI instead, then the script would have been executed
   with the same values for the SCRIPT_NAME, PATH_INFO and QUERY_STRING
   meta-variables.  The Script-URI has the structure of a generic URI as
   defined in section 3 of RFC 2396 [2], with the exception that object
   parameters and fragment identifiers are not permitted.  The various
   components of the Script-URI are defined by some of the
   meta-variables (see below);

      script-URI =  "://" <server-name> ":" <server-port>
                   <script-path>  "?" <query-string>

   where  is found from SERVER_PROTOCOL, <server-name>,
   <server-port> and <query-string> are the values of the respective