Augmented BNF for Syntax Specifications: ABNF
draft-crocker-abnf-v3-00

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Last updated 2002-06-25
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at
https://www.ietf.org/archive/id/draft-crocker-abnf-v3-00.txt

Abstract

Internet technical specifications often need to define a format syntax and are free to employ whatever notation their authors deem useful. Over the years, a modified version of Backus-Naur Form (BNF), called Augmented BNF (ABNF), has been popular among many Internet specifications. It balances compactness and simplicity, with reasonable representational power. In the early days of the Arpanet, each specification contained its own definition of ABNF. This included the email specifications, [RFC733] and then [RFC822] which have come to be the common citations for defining ABNF. The current document separates out that definition, to permit selective reference. Predictably, it also provides some modifications and enhancements. The differences between standard BNF and ABNF involve naming rules, repetition, alternatives, order-independence, and value ranges. Appendix A (Core) supplies rule definitions and encoding for a core lexical analyzer of the type common to several Internet specifications. It is provided as a convenience and is otherwise separate from the meta language defined in the body of this document, and separate from its formal status.

Authors

Dave Crocker (dcrocker@bbiw.net)
Paul Overell (paulo@turnpike.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)