ISO/IEC INTERNATIONAL STANDARD 14977 First edition 1996-12-15 Information technology ---- Syntactic metalanguage Extended BNF Technologies de I'information -Métalangage syntaxique-BNF étendu S E 0 Reference number ISO/IEC 14977:1996(E) Copyright Intermational Organization for Standardization rmitted without license from IHS Not for Resale ISO/IEC 14977 : 1996(E) Contents Page Foreword iv Introduction 1 Scope. 1 2 Normative references 1 3 Definitions 1 4 The form of each syntactic element of Extended BNF 1 4.1 General 2 4.2 Syntax 2 4.3 Syntax-rule 2 4.4 Definitions-list . 2 4.5 Single-definition . 2 4.6 Syntactic-term 2 4.7 Syntactic exception 2 4.8 Syntactic-factor 2 4.9 Integer 2 4.10 Syntactic-primary 2 4.11 Optional-sequence 3 4.12 Repeated sequence 3 4.13 Grouped sequence 3 4.14 Meta-identifier . 3 4.15 Meta-identifier-character 3 4.16 Terminal-string. . 3 4.17 First-terminal-character 3 4.18 Second-terminal-character 3 4.19 Special-sequence 4.20 Speciai-sequence-character 3 4.21 Empty-sequence 3 4.22 Further examples 3 @ ISO/IEC 1996 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. ISO/IEC Copyright Office · Case Postale 56 . CH-1211 Geneve 20 . Switzerland Printed in Switzerland ii Copyight Intematinal Organizationfor Standardization nse with IS nitted without license from IHS Not for Resale ISO/IEC 14977 : 1996(E) @ ISO/IEC 5 The symbols represented by each syntactic eiement. 5.1 General 3 5.2 Terminai-string. 4 5.3 Meta-identifier. 4 5.4 Grouped-sequence 4 5.5 Optional-sequence 4 5.6 Repeated-sequence 4 5.7 Syntactic-factor 4 5.8 Syntactic-term 4 5.9 Single-definition . 5 5.10 Definitions-list 5 5.11 s Special-sequence 5 5.12 Empty-sequence 5 6 Layout and Comments 5 6.1 5 6.2 Terminal-character 5 6.3 Gap-free-symbol 6 6.4 Gap-separator 6 6.5 Commentiess-symboi 6 6.6 Comment-symbol . . 6 6.7 Bracketed-textual-comment 6 The representation of each terminal-character in Extended BNF 6 7.1 General . 6 7.2 Letters and digits 6 7.3 Other terminal characters 6 7.4 Alternative representations . 6 7.5 Other-character 7 7.6 Gap-separator 7 7.7 Terminal-characters represented by a pair of characters 8 7.8 Invalid character sequences 8 8 Examples 8 8.1 The syntax of Extended BNF 8 8.2 Extended BNF used to define itself informally 10 8.3 Extended BNF defined informally 10 Annexes A Two-level grammars 11 B Bibliography 12 iii Copyright Intemational Organization for Standardization ense from IHS Not for Resale