VRML97, ISO/IEC 14772-1:1997 -- Annex A, Grammar

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The Virtual Reality Modeling Language

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Annex A
(normative)

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Grammar definition

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## A.1 Table of contents and introduction

### A.1.1 Table of contents

This annex provides a detailed description of the grammar for each syntactic element in this part of ISO/IEC 14772. The following table of contents lists the topics in this clause:

A.1 Table of contents and introduction
A.1.1 Table of contents
A.1.2 Introduction
A.2 General
A.3 Nodes
A.4 Fields

### A.1.2 Introduction

It is not possible to parse VRML files using a context-free grammar. Semantic knowledge of the names and types of fields, eventIns, and eventOuts for each node type (either built-in or user-defined using PROTO or EXTERNPROTO) shall be used during parsing so that the parser knows which field type is being parsed.

The '#' (0x23) character begins a comment wherever it appears outside of the first line of the VRML file or quoted SFString or MFString fields. The '#' character and all characters until the next line terminator comprise the comment and are treated as whitespace.

The carriage return (0x0d), linefeed (0x0a), space (0x20), tab (0x09), and comma (0x2c) characters are whitespace characters wherever they appear outside of quoted SFString or MFString fields. Any number of whitespace characters and comments may be used to separate the syntactic entities of a VRML file. All reserved keywords are displayed in boldface type.

Any characters (including linefeed and '#') may appear within the quotes of SFString and MFString fields. A double quote character within a string shall be preceded with a backslash (e.g, "Each double quotes character \" shall have a backslash."). A backslash character within a string shall be preceded with a backslash forming two backslashes (e.g., "One backslash \\ character").

Clause 6, Nodes reference, contains a description of the allowed fields, eventIns and eventOuts for all pre-defined node types. The double, float, and int32 symbols are expressed using Perl regular expression syntax; see E.[PERL] for details. The IdFirstChar, IdRestChars, and string symbols have not been formally specified; Clause 5, Fields and events reference, contains a more complete description of their syntax.

The following conventions are used in the semi-formal grammar specified in this clause:

1. Keywords and terminal symbols which appear literally in the VRML file, are specified in bold.
2. Nonterminal symbols used in the grammar are specified in italic.
3. Production rules begin with a nonterminal symbol and the sequence of characters "::=", and end with a semi-colon (";").
4. Alternation for production rules is specified using the vertical-bar symbol ("|").

Table A.1 contains the complete list of lexical elements for the grammar in this part of ISO/IEC 14772.

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Table A.1 -- VRML lexical elements

Keywords | Terminal symbols | Other symbols
DEF EXTERNPROTO FALSE IS NULL PROTO ROUTE TO TRUE USE eventIn eventOut exposedField field | period (.) open brace ({) close brace (}) open bracket ([) close bracket (]) | Id double fieldType float int32 string

Terminal symbols and the string symbol may be separated by one or more whitespace characters. Keywords and the Id, fieldType, float, int32, and double symbols shall be separated by one or more whitespace characters.

## A.2 General

vrmlScene ::=
  statements ;
statements ::=
  statement |
  statement statements |
  empty ;
statement ::=
  nodeStatement |
  protoStatement |
  routeStatement ;
nodeStatement ::=
  node |
  DEF nodeNameId node |
  USE nodeNameId ;
rootNodeStatement ::=
  node | DEF nodeNameId node ;
protoStatement ::=
  proto |
  externproto ;
protoStatements ::=
  protoStatement |
  protoStatement protoStatements |
  empty ;
proto ::=
  PROTO nodeTypeId [ interfaceDeclarations ] { protoBody } ;
protoBody ::=
  protoStatements rootNodeStatement statements ;
interfaceDeclarations ::=
  interfaceDeclaration |
  interfaceDeclaration interfaceDeclarations |
  empty ;
restrictedInterfaceDeclaration ::=
  eventIn fieldType eventInId |
  eventOut fieldType eventOutId |
  field fieldType fieldId fieldValue ;
interfaceDeclaration ::=
  restrictedInterfaceDeclaration |
  exposedField fieldType fieldId fieldValue ;
externproto ::=
  EXTERNPROTO nodeTypeId [ externInterfaceDeclarations ] URLList ;
externInterfaceDeclarations ::=
  externInterfaceDeclaration |
  externInterfaceDeclaration externInterfaceDeclarations |
  empty ;
externInterfaceDeclaration ::=
  eventIn fieldType eventInId |
  eventOut fieldType eventOutId |
  field fieldType fieldId |
  exposedField fieldType fieldId ;
routeStatement ::=
  ROUTE nodeNameId . eventOutId TO nodeNameId . eventInId ;
URLList ::=
  mfstringValue ;
empty ::=
  ;

## A.3 Nodes

node ::=
  nodeTypeId { nodeBody } |
  Script { scriptBody } ;
nodeBody ::=
  nodeBodyElement |
  nodeBodyElement nodeBody |
  empty ;
scriptBody ::=
  scriptBodyElement |
  scriptBodyElement scriptBody |
  empty ;
scriptBodyElement ::=
  nodeBodyElement |
  restrictedInterfaceDeclaration |
  eventIn fieldType eventInId IS eventInId |
  eventOut fieldType eventOutId IS eventOutId |
  field fieldType fieldId IS fieldId ;
nodeBodyElement ::=
  fieldId fieldValue |
  fieldId IS fieldId |
  eventInId IS eventInId |
  eventOutId IS eventOutId |
  routeStatement |
  protoStatement ;
nodeNameId ::=
  Id ;
nodeTypeId ::=
  Id ;
fieldId ::=
  Id ;
eventInId ::=
  Id ;
eventOutId ::=
  Id ;
Id ::=
  IdFirstChar |
  IdFirstChar IdRestChars ;
IdFirstChar ::=
  Any ISO-10646 character encoded using UTF-8 except: 0x30-0x39, 0x0-0x20, 0x22, 0x23, 0x27, 0x2b, 0x2c, 0x2d, 0x2e, 0x5b, 0x5c, 0x5d, 0x7b, 0x7d, 0x7f ;
IdRestChars ::=
  Any number of ISO-10646 characters except: 0x0-0x20, 0x22, 0x23, 0x27, 0x2c, 0x2e, 0x5b, 0x5c, 0x5d, 0x7b, 0x7d, 0x7f ;

## A.4 Fields

fieldType ::=
  MFColor |
  MFFloat |
  MFInt32 |
  MFNode |
  MFRotation |
  MFString |
  MFTime |
  MFVec2f |
  MFVec3f |
  SFBool |
  SFColor |
  SFFloat |
  SFImage |
  SFInt32 |
  SFNode |
  SFRotation |
  SFString |
  SFTime |
  SFVec2f |
  SFVec3f ;
fieldValue ::=
  sfboolValue |
  sfcolorValue |
  sffloatValue |
  sfimageValue |
  sfint32Value |
  sfnodeValue |
  sfrotationValue |
  sfstringValue |
  sftimeValue |
  sfvec2fValue |
  sfvec3fValue |
  mfcolorValue |
  mffloatValue |
  mfint32Value |
  mfnodeValue |
  mfrotationValue |
  mfstringValue |
  mftimeValue |
  mfvec2fValue |
  mfvec3fValue ;
sfboolValue ::=
  TRUE |
  FALSE ;
sfcolorValue ::=
  float float float ;
sffloatValue ::=
  float ;
float ::=
  ([+/-]?((([0-9]+(\.)?)|([0-9]*\.[0-9]+))([eE][+\-]?[0-9]+)?)).
sfimageValue ::=
  int32 int32 int32 ...
sfint32Value ::=
  int32 ;
int32 ::=
  ([+\-]?(([0-9]+)|(0[xX][0-9a-fA-F]+)))
sfnodeValue ::=
  nodeStatement |
  NULL ;
sfrotationValue ::=
  float float float float ;
sfstringValue ::=
  string ;
string ::=
  ".*" ... double-quotes must be \", backslashes must be \\...
sftimeValue ::=
  double ;
double ::=
  ([+/-]?((([0-9]+(\.)?)|([0-9]*\.[0-9]+))([eE][+\-]?[0-9]+)?))
mftimeValue ::=
  sftimeValue |
  [ ] |
  [ sftimeValues ] ;
sftimeValues ::=
  sftimeValue |
  sftimeValue sftimeValues ;
sfvec2fValue ::=
  float float ;
sfvec3fValue ::=
  float float float ;
mfcolorValue ::=
  sfcolorValue |
  [ ] |
  [ sfcolorValues ] ;
sfcolorValues ::=
  sfcolorValue |
  sfcolorValue sfcolorValues ;
mffloatValue ::=
  sffloatValue |
  [ ] |
  [ sffloatValues ] ;
sffloatValues ::=
  sffloatValue |
  sffloatValue sffloatValues ;
mfint32Value ::=
  sfint32Value |
  [ ] |
  [ sfint32Values ] ;
sfint32Values ::=
  sfint32Value |
  sfint32Value sfint32Values ;
mfnodeValue ::=
  nodeStatement |
  [ ] |
  [ nodeStatements ] ;
nodeStatements ::=
  nodeStatement |
  nodeStatement nodeStatements ;
mfrotationValue ::=
  sfrotationValue |
  [ ] |
  [ sfrotationValues ] ;
sfrotationValues ::=
  sfrotationValue |
  sfrotationValue sfrotationValues ;
mfstringValue ::=
  sfstringValue |
  [ ] |
  [ sfstringValues ] ;
sfstringValues ::=
  sfstringValue |
  sfstringValue sfstringValues ;
mfvec2fValue ::=
  sfvec2fValue |
  [ ] |
  [ sfvec2fValues] ;
sfvec2fValues ::=
  sfvec2fValue |
  sfvec2fValue sfvec2fValues ;
mfvec3fValue ::=
  sfvec3fValue |
  [ ] |
  [ sfvec3fValues ] ;
sfvec3fValues ::=
  sfvec3fValue |
  sfvec3fValue sfvec3fValues ;

Questions or comments.
Copyright © 1997 The VRML Consortium Incorporated.
`http://www.vrml.org/Specifications/VRML97/part1/grammar.html`