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EBNF

• ISO 14977
  • Information technology -- Syntactic metalanguage -- Extended BNF

Production  = name "=" [ Expression ] ";" ;
Expression  = Alternative { "|" Alternative } ;
Alternative = Term { Term } ;
Term        = name | TOKEN | Group | Option | Repetition ;
Group       = "(" Expression ")" ;
Option      = "[" Expression "]" ;
Repetition  = "{" Expression "}" ;