Comprehensive Core Rules and References for ABNF

The information below is for an old version of the document
Document Type Active Internet-Draft (individual in art area)
Last updated 2016-09-20
Stream IETF
Intended RFC status Proposed Standard
Formats plain text pdf html bibtex
Stream WG state (None)
Document shepherd No shepherd assigned
IESG IESG state I-D Exists (IESG: Dead)
Consensus Boilerplate Unknown
Telechat date
Responsible AD Alexey Melnikov
Send notices to (None)
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

   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
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF). Note that other groups may also distribute working
   documents as Internet-Drafts. The list of current Internet-Drafts is

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 24, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Leonard                     Standards Track                     [Page 1]
Internet-Draft              More Core Rules               September 2016

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

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]
Internet-Draft              More Core Rules               September 2016

   the "@" specifies the name of the rule in the reference containing
   ABNF. The <ruleref> production following the "@" specifies the
   reference containing the rule. This specification does not define the
Show full document text