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Title : Augmented BNF for Syntax Specifications: ABNF
Author(s) : D. Crocker, P. Overell
Filename : draft-crocker-abnf-v3-00.txt
Date : 25-Jun-02
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
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