Metasyntax

Although many different metasyntaxes are possible, Backus-Naur form (BNF), Wirth Syntax Notation (WSN), Extended Backus-Naur form (EBNF), and Augmented Backus-Naur form (ABNF), which express syntax as a set of derivation rules, are almost universally used. The variables in these metasyntaxes are properly known as metasyntactic variables, although the term is used informally in other ways.

See also

• Attribute grammar
• Two-level grammar