Comprehensive Core Rules and References for ABNF
draft-seantek-abnf-more-core-rules-06

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Document Type Active Internet-Draft (individual in art area)
Last updated 2016-09-20
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Network Working Group                                         S. Leonard
Internet-Draft                                             Penango, Inc.
Updates: 5234 (if approved)                           September 20, 2016
Intended Status: Standards Track                                        
Expires: March 24, 2017                                                 

            Comprehensive Core Rules and References for ABNF
                 draft-seantek-abnf-more-core-rules-06
                                    
Abstract

   This document extends the base definition of ABNF (Augmented Backus-
   Naur Form) to include comprehensive support for certain symbols
   related to ASCII, and defines a reference syntax.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on March 24, 2017.

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Leonard                     Standards Track                     [Page 1]
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1.  Introduction

   Augmented Backus-Naur Form (ABNF) [RFC5234] is a formal syntax that
   is popular among many Internet specifications. Many Internet
   documents employ this syntax along with the Core Rules defined in
   Appendix B.1 of [RFC5234]. However, the Core Rules do not specify
   many symbols in the ASCII range that are also needed by these relying
   documents, forcing document authors to define them as local rules.
   Sometimes different documents define these common symbols in
   different ways, resulting in confusion or incompatibility when the
   rules are misread or are combined with other sets of rules.
   Furthermore, [RFC5234] does not clarify whether referencing [RFC5234]
   for ABNF automatically defines its Core Rules.

   [RFC5234] also lacks a syntax for referring to rules from other
   specifications. Instead, authors have been required to name the rules
   and sources in the specification prose. While this method has served
   authors well, it has hampered machine-readable ABNF efforts for
   services such as syntax highlighting, automatic grammar checking, and
   compiling into target computer languages.

2.  Comprehensive Core Rule Update

   This document provides Core Rules that include comprehensive support
   for certain symbols, namely DELETE (DEL) and the C0 controls in
   [ASCII86], which for purposes of this document is equivalent to
   [RFC0020].

3. Reference Syntax

   To reference a rule in another ABNF grammar, use the syntax
   rulename@REF. The referenced rule resolves to terminal values in the
   context of the referenced ABNF grammar, essentially replacing the
   verbiage: "{RULE} is taken from [{Section X} of] {[RFCXXXX]}" in
   prose specification text that introduces the ABNF. The following
   enhancement to [RFC5234] permits this referenced-rule syntax as a
   change to the <element> production:

      element        =  rulename [ "@" ruleref ] / group / option
                        char-val / num-val / prose-val

      ruleref        =  ref-doc / ref-path

      ref-doc        =  "[" 1*(%x20-5A / %x5C / %x5E-7E / ref-doc) "]"

      ref-path       =  "<" 1*(%x20-3B / "<" / "=" / ">" / %x3F-7E) ">"

   In a referenced-rule production the <rulename> production preceding
 

Leonard                     Standards Track                     [Page 2]
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