The Virtual Reality Modeling Language Specification

Appendix A. Grammar Definition

Version 2.0, ISO/IEC 14772

August 4, 1996

This section provides a detailed description of the grammar for each node in VRML 2.0. There are four sections: Introduction, General, Nodes, and Fields.

A.1 Introduction

VRML grammar is ambiguous; semantic knowledge of the names and types of fields, eventIns, and eventOuts for each node type (either builtIn or user-defined using PROTO or EXTERNROTO) must 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 quoted SFString or MFString fields. The '#' character and all characters until the next carriage-return or newline make up the comment and are treated as whitespace.

The carriage return (0x0d), newline (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.

Please see the Nodes Reference section of the Moving Worlds specification for a description of the allowed fields, eventIns and eventOuts for all pre-defined node types. Also note that some of the basic types that will typically be handled by a lexical analyzer (sffloatValue, sftimeValue, sfint32Value, and sfstringValue) have not been formally specified; please see the Fields Reference section of the spec for a more complete description of their syntax.

A.2 General

vrmlScene:: declarations
declarations:: declaration; declaration declarations
declaration:: nodeDeclaration; protoDeclaration; routeDeclaration; NULL
nodeDeclaration:: node; DEF nodeNameId node; USE nodeNameId
protoDeclaration:: proto; externproto
proto:: PROTO nodeTypeId [ interface_declarations ] { vrmlScene }
interfaceDeclarations:: interfaceDeclaration; interfaceDeclaration interfaceDeclarations
restrictedInterfaceDeclaration:: eventIn fieldType eventInId; eventOut fieldType eventOutId; field fieldType fieldId fieldValue
interfaceDeclaration:: restrictedInterfaceDeclaration; exposedField fieldType fieldId fieldValue
externproto:: EXTERNPROTO nodeTypeId [ externInterfaceDeclarations ] mfstringValue
externInterfaceDeclarations:: externInterfaceDeclaration; externInterfaceDeclaration externInterfaceDeclarations
externInterfaceDeclaration:: eventIn fieldType eventInId; eventOut fieldType eventOutId; field fieldType fieldId; exposedField fieldType fieldId
routeDeclaration:: ROUTE nodeNameId . eventOutId TO nodeNameId . eventInId

A.3 Nodes

node:: nodeTypeId { nodeGuts }; Script { scriptGuts }
nodeGuts:: nodeGut; nodeGut nodeGuts
scriptGuts:: scriptGut; scriptGut scriptGuts
scriptGut:: nodeGut; restrictedInterfaceDeclaration; eventIn fieldType eventInId IS eventInId; eventOut fieldType eventOutId IS eventOutId; field fieldType fieldId IS fieldId
nodeGut:: fieldId fieldValue; fieldId IS fieldId; eventInId IS eventInId; eventOutId IS eventOutId; routeDeclaration; protoDeclaration
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, 0x2c, 0x2e, 0x5b, 0x5c, 0x5d, 0x7b, 0x7d.
IdRestChars:: Any number of ISO-10646 characters except: 0x0-0x20, 0x22, 0x23, 0x27, 0x2c, 0x2e, 0x5b, 0x5c, 0x5d, 0x7b, 0x7d.

A.4 Fields

fieldType:: MFColor; MFFloat; MFInt32; MFNode; MFRotation; MFString; 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; mfvec2fValue; mfvec3fValue
sfboolValue:: TRUE; FALSE
sfcolorValue:: float float float
sffloatValue:: ... floating point number in ANSI C floating point format...
sfimageValue:: int32 int32 int32 int32s...
sfint32Value:: [0-9]+; 0x[0-9A-F]+
sfnodeValue:: nodeDeclaration; NULL
sfrotationValue:: float float float float
sfstringValue:: ".*" ... double-quotes must be \", backslashes must be \\...
sftimeValue:: ... double-precision number in ANSI C floating point format...
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:: nodeDeclaration; [ ]; [ nodeDeclarations ]
nodeDeclarations:: nodeDeclaration; nodeDeclaration nodeDeclarations
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