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Special Sequence Format

Topic Overview

Purpose

This topic explains the format of the special sequence sections in the EBNF file used to configure the grammar.

Required background

The following topics are prerequisites to understanding this topic:

Topic	Purpose
Syntax Parsing Engine Overview	This topic provides an overview of the Syntax Parsing Engine.
Grammar Overview	This topic provides an overview of the Syntax Parsing Engine’s Grammar.
Grammar Analysis	This topic explains the grammar analysis performed by the Syntax Parsing Engine.
EBNF File Format Overview	This topic gives an overview of the EBNF file format used to define a grammar.

In this topic

This topic contains the following sections:

Special Sequence Sections Overview
Special Sequence Section Types
Grammar Properties Section
Non-Terminal Symbol Attributes Sections
Related Content

Special Sequence Sections Overview

Special sequence sections summary

By using the EBNF format supported by the Syntax Parsing Engine you can supply a lot of descriptive information about grammar instance, lexer states, terminal symbols, and non-terminal symbols.

This information is specified using XML within special sequences of the EBNF file.

Special Sequence Section Types

Special sequence sections summary chart

Section	Details
Grammar Properties Section	The grammar properties section defines the grammar, lexer states, and terminal symbols and is allowed only at the top of an EBNF file.
Non-Terminal Symbol Attributes Sections	This section is used to set specific properties on the `NonTerminalSymbol` instance defined by the next rule.

Grammar Properties Section

Overview

The grammar properties section defines the grammar, lexer states, and terminal symbols and is allowed only at the top of an EBNF file. There can be only one grammar properties section.

Elements

The following tables list all elements allowed in the grammar properties section with their respective parent/child relations:

Grammar element:

Description: defines everything in a Grammar instance except the non-terminal symbols and syntax rule trees, which are done in the normal EBNF format.

Parent elements: (none)

Attribute	Type	* Description*
EndOfStreamSymbolName	String	(optional) The value for the Grammar.EndOfStreamSymbolName property. If not specified, the value will be “EndOfStreamToken”.
Name	String	(optional) The value for the Grammar.Name property. If not specified, the value will be null.
NewLineSymbolName	String	(optional) The value for the Grammar.NewLineSymbolName property. If not specified, the value will be “NewLineToken”
StartSymbol	String	(optional) The name of the NonTerminalSymbol which should be set as the Grammar.StartSymbol value. If not specified, the first non-terminal symbol defined in the file will be used as the start symbol.
SupportsParsing	bool	(optional) The value for the Grammar.SupportsParsing property. If not specified, the value will be True.
SyntaxTreePruningMode	SyntaxTreePruningMode	(optional) The value for the Grammar.SyntaxTreePruningMode property. If not specified, the value will be BasedOnChildrenAndName.
UnrecognizedSymbolName	String	(optional) The value for the Grammar.UnrecognizedSymbolName property. If not specified, the value will be “UnrecognizedToken”.
WhitespaceSymbolName	String	(optional) The value for the Grammar.WhitespaceSymbolName property. If not specified, the value will be “WhitespaceToken”.
WhitespacePattern	String	(optional) The value of the Grammar.WhitespacePattern property. If not specified, the value will be “[ \t]+”.

Child Element	* Description*
TerminalSymbol	Defines a TerminalSymbol and adds it to the default LexerState of the grammar (Grammar.LexerStates.DefaultLexerState).
`TerminalSymbolReference`	Adds an existing TerminalSymbol to the default LexerState of the grammar.

TerminalSymbol element:

Description: Creates a new TerminalSymbol instance and adds it to the owning lexer state.

Parent Elements: Grammar, LexerState

Attribute Type * Description*

Comparison

TerminalSymbolComparison

(optional) The value indicating how the Value attribute should be interpreted. Possible values are Literal, LiteralIgnoreCase, and RegularExpression. If not specified, the value will be Literal.

IsExitSymbol

bool

(optional) Indicates whether the new TerminalSymbol should be added to its owning lexer state as an exit symbol. See the Lexical Analysis Overview topic for more information on exit symbols.

IsLookaheadNegative

bool

(optional) The value for the TerminalSymbol. IsLookaheadNegative property, which indicates whether the LookaheadPattern specifies a positive or negative lookahead. If not specified, the value will be False.

IsSignificant

bool?

(optional) The value for the TerminalSymbol.IsSignificant property. If not specified, the value will be null.

IsStartOfErrorRecoveryPair

bool

(optional) The value for the TerminalSymbol.IsStartOfErrorRecoveryPair property. If not specified, the value will be False.

LanguageElementName

String

(optional) The value for the TerminalSymbol. LanguageElementName property. If not specified, the value will be “Undefined”.

LexerStateToEnter

String

(optional) The name of the existing LexerState which should be set as the TerminalSymbol. LexerStateToEnter property. If not specified, the value will be null.

Note	Note The lexer state with the specified name may be defined before or after the `LexerStateToEnter` attribute in the document.

LookaheadPattern

String

(optional) The value for the TerminalSymbol.LookaheadPattern property, which is a regular expression that makes an assertion about the text that should or should not follow a token associated with this terminal symbol. If not specified, the value will be null.

Name

String

(required) The value for the TerminalSymbol.Name property.

Value

String

(optional) The value for the TerminalSymbol.Value property. If not specified, the value from the Name attribute will be used.

Child Element	* Description*
`LexerState`	Defines a `LexerState`, adds it to the `Grammar.LexerStates` collection, and sets that `LexerState` instance as the `TerminalSymbol.LexerStateToEnter` value.

TerminalSymbolReference element

Description: Adds an existing TerminalSymbol instance to the owning lexer state.

Note	Note The definition for the referenced `TerminalSymbol` may occur before or after this element in the document.

Parent Elements: Grammar, LexerState

Attribute	Type	* Description*
`IsExitSymbol`	bool	(optional) Indicates whether the new TerminalSymbol should be added to its owning lexer state as an exit symbol or not. See the Lexical Analysis Overview topic for more information on exit symbols.
Name	String	(required) The name of the existing `TerminalSymbol` instance to add to the owning lexer state.

LexerState element

Description: Defines a new LexerState instance and adds it to the Grammar.LexerStates collection.

Parent Elements: TerminalSymbol

Attribute	Type	* Description*
Name	String	(required) The name of the new `LexerState` instance.

Child Element	* Description*
`TerminalSymbol`	Defines a `TerminalSymbol` and adds it to the parent `LexerState`.
`TerminalSymbolReference`	Adds an existing `TerminalSymbol` to the parent `LexerState`.

Example

The following is an example of a grammar properties section:

?
<Grammar Name="My Custom Grammar" NewLineSymbolName="LineBreakToken">
    <TerminalSymbolReference Name="LineBreakToken" />
    <TerminalSymbolReference Name="WhitespaceToken" />
    <TerminalSymbol Name="Word" Value="[\w]+" Comparison="RegularExpression" />
    <TerminalSymbol Name="Punctuation" Value="\W" Comparison="RegularExpression" />
    <TerminalSymbol Name="DoubleQuote" Value="&quot;" LanguageElementName="StringLiteral">
        <LexerState Name="StringLiteral">
            <TerminalSymbol Name="StringLiteralContent" Value="([^&quot;\\\r\n]|(\\[^\r\n]))+"
                Comparison="RegularExpression"LanguageElementName="StringLiteral" />
            <TerminalSymbolReference Name="LineBreakToken" IsExitSymbol="true" />
            <TerminalSymbolReference Name="DoubleQuote" IsExitSymbol="true" />
        </LexerState>
    </TerminalSymbol>
</Grammar>
?

Non-Terminal Symbol Attributes Sections

Overview

The non-terminal symbol attributes sections are allowed immediately before any non-terminal symbol definition. This section is used to set specific properties that will apply only to the next NonTerminalSymbol instance defined.

Elements

The following table lists all attributes for the NonTerminalSymbolOptions element:

Attribute	Type	* Description*
HasPriority	bool	(optional) The value for the `NonTerminalSymbol.HasPriority` property. If not specified, the value will be False.
IsError	bool	(optional) The value for the `NonTerminalSymbol.IsError` property. If not specified, the value will be False.
IsStartOfErrorRecoveryPair	bool	(optional) The value for the `NonTerminalSymbol.IsStartOfErrorRecoveryPair` property. If not specified, the value will be False.
PreventPruning	bool	(optional) The value for the `NonTerminalSymbol.PreventPruning` property. If not specified, the value will be False.
SuppressAmbiguityWarnings	bool	(optional) The value for the `NonTerminalSymbol.SuppressAmbiguityWarnings` property. If not specified, the value will be False.
`SuppressErrorRecoveryForSymbols`	string	(optional) A comma separated list of the names of symbols which should be passed to the NonTerminalSymbol.SuppressErrorRecoveryForSymbol method. The named symbols can be defined before or after the `NonTerminalSymbol`.

Example

The following is an example of a non-terminal symbol definition along with its attributes section defined with XML between the “?” characters :

Document = {Sentence};
?<NonTerminalSymbolOptions SuppressErrorRecoveryForSymbols="Punctuation" />?
Sentence = {Word | StringLiteral}-, Punctuation;
StringLiteral = DoubleQuote, [StringLiteralContent], DoubleQuote;

Topic	Purpose
EBNF Specification Deviations	This topic explains the deviations from the ISO 14977 specification in the EBNF format used by the Syntax Parsing Engine.
Generate Grammar From an EBNF File	This topic explains the process of creating a grammar from EBNF content.
Generate EBNF File From a Grammar	This topic explains the process of creating EBNF content from a grammar.

Windows Forms | Help Topics

Special Sequence Format

Topic Overview

Purpose

Required background

In this topic

Special Sequence Sections Overview

Special sequence sections summary

Special Sequence Section Types

Special sequence sections summary chart

Grammar Properties Section

Overview

Elements

Example

Non-Terminal Symbol Attributes Sections

Overview

Elements

Example

Related Content

Topics