RFC 5234: Augmented BNF for Syntax Specifications: ABNF
In plain English — editorial summary, not part of the RFC
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]
Document record
- Document ID
- RFC5234
- Published
- January 2008
- Authors
- D. Crocker; P. Overell
- Status
- INTERNET STANDARD
- Stream
- IETF
- Area
- —
- Pages
- 16
- Also known as
- STD68
Topics
Standards lineage
This document is one revision in a chain of 3 RFCs, each formally replacing the one before it.
- RFC 2234 (1997)
- RFC 4234 (2005)
- RFC 5234 (2008)
Read the full history of Augmented BNF for Syntax Specifications: ABNF →
Referenced by
One later RFC formally updates or obsoletes part of this document.
Related documents
Ranked automatically by shared keywords, IETF area and stream — not by editorial selection.
- RFC 5137ASCII Escaping of Unicode CharactersCurrent
February 2008
- RFC 5954Essential Correction for IPv6 ABNF and URI Comparison in RFC 3261Current
August 2010
- RFC 3284The VCDIFF Generic Differencing and Compression Data FormatCurrent
July 2002
- RFC 7433A Mechanism for Transporting User-to-User Call Control Information in SIPCurrent
January 2015
- RFC 2910Internet Printing Protocol/1.1: Encoding and TransportObsoleted
September 2000
- RFC 7713Congestion Exposure (ConEx) Concepts, Abstract Mechanism, and RequirementsCurrent
December 2015
- RFC 7913P-Access-Network-Info ABNF UpdateCurrent
June 2016
- RFC 2304Minimal FAX address format in Internet MailObsoleted
March 1998
Also filed under
About this page
The document record above — title, authors, date, status, stream, area, relationships, DOI and errata — is imported verbatim from the public RFC Editor index. The “in plain English” section is editorial: written by The metasystema editorial team, not part of the RFC. Where the two differ, the RFC text governs.
Last checked against the RFC Editor index on . RFCs are never revised after publication; changes are issued as new documents.
Data sources · Editorial policy · Report a correction · What is an RFC?