Augmented BNF for Syntax Specifications: ABNF, October 2005
- Canonical URL:
- File formats:
- DRAFT STANDARD
- RFC 2234
- Obsoleted by:
- RFC 5234
- D. Crocker, Ed.
- NON WORKING GROUP
Discuss this RFC: Send questions or comments to firstname.lastname@example.org
Internet technical specifications often need to define a formal syntax. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. The current specification documents ABNF. It balances compactness and simplicity, with reasonable representational power. The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges. This specification also supplies additional rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. [STANDARDS-TRACK]
For the definition of Status, see RFC 2026.
For the definition of Stream, see RFC 4844.