The following figure shows a sample of a complex syntax description. This is not an example of an exis- ting system parameter or panel command. It is used mainly to demonstrate the “look and feel” of syntax descriptions.

  CMDNAME required argument [optional argument]
          {required choice 1 | required choice 2 | required choice 3}
          [optional choice 1 | optional choice 2]
          REQUIRED KEYWORD=variable
          [OPTIONAL KEYWORD=variable]
          [DEFAULT KEYWORD | KEYWORD 1 | KEYWORD 2]
          [KEYWORD=default choice | KEYWORD={choice 1 | choice 2}]
          repeatable item n {repeatable item n ...}
          repeatable item n {,repeatable item n ,...}
          fragment name
          (variable 1, variable 2)
          
      fragment_name
          [DEFAULT KEYWORD | KEYWORD 1 | KEYWORD 2 | KEYWORD 3 | KEYWORD 4]
          KEYWORD={choice 1 | choice 2 | choice 3 | choice 4}

All syntax is described using the Extended Backus-Naur form wherever possible. This article is intended to help content creators understand the formatting and to make them understandable by the readers.

<ebnf> "EBNF defined in itself" {
syntax     = [ title ] "{" { production } "}" [ comment ].
production = identifier "=" expression ( "." | ";" ) .
expression = term { "|" term } .
term       = factor { factor } .
factor     = identifier
           | literal
           | "[" expression "]"
           | "(" expression ")"
           | "{" expression "}" .
identifier = character { character } .
title      = literal .
comment    = literal .
literal    = "'" character { character } "'"
           | '"' character { character } '"' .
}</ebnf>

• See: examples
• EBNF
• Wirth_syntax_notation