system defined

      The feature may differ between systems, but must be the same for
      different implementations using the same system. A system will
      usually identify a class of operating-systems. Some systems are




 
INTERNET-DRAFT       Common Gateway Interface - 1.1     15 February 1996


      defined in section 12 of this document. New systems may be defined
      by new specifications without revision of this document.

   implementation defined

      The behaviour of the feature may vary from implementation to
      implementation, but a particular implementation must document its
      behaviour.

1.4. Terminology

   This specification uses many terms defined in the HTTP/1.0
   specification [3]; however, the following terms are used here in a
   sense which may not accord with their definitions in that document,
   or with their common meaning.

   environment variable

      A named parameter that carries information from the server to the
      script. It is not necessarily a variable in the operating-system's
      environment, although that is the most common implementation.

   script

      The software which is invoked by the server via this interface. It
      need not be a standalone program, but could be a
      dynamically-loaded or shared library, or even a subroutine in the
      server.

   server

      The application program which invokes the script in order to
      service requests.

2. Notational Conventions and Generic Grammar

2.1. Augmented BNF

   All of the mechanisms specified in this document are described in
   both prose and an augmented Backus-Naur Form (BNF) similar to that
   used by RFC 822 [6]. This augmented BNF contains the following
   constructs:

   name = definition

      The name of a rule is simply the name itself; it is separated from
      the definition by the equal character ("="). Whitespace is only
      significant in that continuation lines of a definition are




 
INTERNET-DRAFT       Common Gateway Interface - 1.1     15 February 1996


      indented.

   "literal"

      Quotation marks (") surround literal text, except for a literal
      quotation mark, which is surrounded by angle-brackets ("<" and
      ">").  Unless stated otherwise, the text is case-sensitive.

   rule1 | rule2

      Alternative rules are separated by a vertical bar ("|").

   (rule1 rule2 rule3)

      Elements enclosed in parentheses are treated as a single element.

   *rule

      A rule preceded by an asterisk ("*") may have zero or more
      occurrences. A rule preceded by an integer followed by an asterisk
      must occur at least the specified number of times.

   [rule]

      A element enclosed in square brackets ("[" and "]") is optional.

2.2. Basic Rules

   The following rules are used throughout this specification to
   describe basic parsing constructs.