Syntax for Format Definitions

 It does require that documents making use of such provide a normative reference to a document laying out the syntax. The IESG recommends that authors choose a syntax for which automated validation is available, as an aid to production and review. At the time of this statement, ABNF is most common in Standards Track RFCs, and authors are encouraged to review draft-crocker-abnf-rfc2234bis-00.txt.