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Augmented BNF for Syntax Specifications: ABNF (RFC2234)

IP.com Disclosure Number: IPCOM000002793D
Original Publication Date: 1997-Nov-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 11 page(s) / 22K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

D. Crocker: AUTHOR [+3]

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.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 12% of the total text.

Network Working Group D. Crocker, Ed.

Request for Comments: 2234 Internet Mail Consortium

Category: Standards Track P. Overell

Demon Internet Ltd.

November 1997

Augmented BNF for Syntax Specifications: ABNF

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1997). All Rights Reserved.

TABLE OF CONTENTS

1. INTRODUCTION .................................................. 2

2. RULE DEFINITION ............................................... 2

2.1 RULE NAMING .................................................. 2

2.2 RULE FORM .................................................... 3

2.3 TERMINAL VALUES .............................................. 3

2.4 EXTERNAL ENCODINGS ........................................... 5

3. OPERATORS ..................................................... 5

3.1 CONCATENATION RULE1 RULE2 ............................. 5

3.2 ALTERNATIVES RULE1 / RULE2 ................................... 6

3.3 INCREMENTAL ALTERNATIVES RULE1 =/ RULE2 .................... 6

3.4 VALUE RANGE ALTERNATIVES %C##-## ........................... 7

3.5 SEQUENCE GROUP (RULE1 RULE2) ................................. 7

3.6 VARIABLE REPETITION *RULE .................................... 8

3.7 SPECIFIC REPETITION NRULE .................................... 8

3.8 OPTIONAL SEQUENCE [RULE] ..................................... 8

3.9 ; COMMENT .................................................... 8

3.10 OPERATOR PRECEDENCE ......................................... 9

4. ABNF DEFINITION OF ABNF ....................................... 9

5. SECURITY CONSIDERATIONS ....................................... 10

6. APPENDIX A - CORE ............................................. 11

6.1 CORE RULES ................................................... 11

6.2 COMMON ENCODING .............................................. 12

7. ACKNOWLEDGMENTS ............................................... 12

8. REFERENCES .................................................... 13

9. CONTACT ..........................................................