The document provides an overview of the structure and syntax of Augmented Backus-Naur Form (ABNF) grammars. It discusses grammar headers, rules, expansions, and advanced features. Key elements include mandatory and optional grammar headers, public and private rules, basic expansions like words and sequences, and advanced features such as repeats, weights, tags, and precedence. The document serves as a primer for understanding the core concepts and components of ABNF grammars.

1. An ABNF PrimerConcepts, structure, syntax

2. IntroductionW3C standard

3. http://www.w3.org/TR/speech-grammar

4. W3C recommandation:

5. March 16th, 2004

6. Defines both the XML form and the Augmented BNF (ABNF) form

7. They are equivalent

8. Supported by a complete development environment

9. NuGram IDECopyright © 2010 Nu Echo Inc.

10. Structure of an ABNF GrammarHeaders#ABNF 1.0 ISO-8859-1;language en-US;mode voice;root$yesOrNo;private$yesOrNo = yes {out.value = 'yes'}| no {out.value = 'no'};RulesCopyright © 2010 Nu Echo Inc.

11. CommentsC/C++/Java Comments

12. // to end of line

13. /* ... */

14. Documentation comments

15. /** ... */

16. @example to document sample sentences

17. Can appear before rule definitions, root header, and language header.Copyright © 2010 Nu Echo Inc.

18. Grammar headersCopyright © 2010 Nu Echo Inc.

19. Grammar HeadersSelf-identifying header

20. Mandatory

21. Encoding is optional

22. Can be preceded by byte order mask (BOM)‏Ex:#ABNF 1.0;#ABNF 1.0 UTF-8;Copyright © 2010 Nu Echo Inc.

23. Grammar HeadersLanguage

24. Identifies the language of the document

25. Required for voice grammars

26. Languages codes defined by RFC 3066Ex:language en;language fr-CA;Copyright © 2010 Nu Echo Inc.

27. Grammar HeadersMode

28. Indicates the type of input

29. Optional header

30. 'dtmf' or 'voice' (default)Ex:mode voice;mode dtmf;Copyright © 2010 Nu Echo Inc.

31. Grammar HeadersRoot

32. Defines the grammar's top-level rule

33. Optional

34. Root rule can be either public or privateEx:root$rootRule;Copyright © 2010 Nu Echo Inc.

35. Grammar HeadersTag-format

36. Declares content type for the semantic tags (actions)‏

37. Value is a URI

38. Recognition-engine specificEx:tag-format <semantics/1.0>; (SISR)tag-format <Nuance>; (Nuance)tag-format <swi-semantics/1.0>; (Nuance)tag-format <semantics-ms/1.0>; (Microsoft)tag-format <semantics/1.0.2006>; (LumenVox)Copyright © 2010 Nu Echo Inc.

39. Grammar HeadersLexicon

40. Specifies a pronunciation lexicon to use (a URI)‏

41. One or more occurrences

42. Format is engine-specificEx:lexicon <../lex/names.pls>;Copyright © 2010 Nu Echo Inc.

43. Grammar HeadersBase URI

44. Base URI for all relative URIs in the document

45. Optional

46. Has precedence over the meta headerEx:base <http://localhost:8080/>;Copyright © 2010 Nu Echo Inc.

47. Grammar HeadersMeta and Http-Equiv

48. Metadata attached to the grammar

49. Properties taking precedence over HTTP headers

50. One or more occurrencesEx:meta“Author”is“J. Doe”;http-equiv“Expires”is“0”;Copyright © 2010 Nu Echo Inc.

51. Relative URI ResolvingBase URI :

52. base header

53. meta“base” header

54. metadata from protocol interaction (ex. HTTP header)‏

55. base URI of the current documentEx:meta“base”is“http://example.com/grammars/date.abnf”;meta“base”is“http://example.com/grammars/”;base “http://example.com/grammars/date.abnf”;Copyright © 2010 Nu Echo Inc.

56. Relative URI ResolvingASR Engines behave differently

57. OSR / Nuance 9

58. Full conformance to RFC 2396 (now obsoleted by RFC 3986)

59. Loquendo ASR

60. Base URI must not contain the document’s name

61. Best practice: always end the URI with a “/”Copyright © 2010 Nu Echo Inc.

62. Grammar rulesCopyright © 2010 Nu Echo Inc.

63. Grammar RulesA rule is an association between a name and an expansion

64. Rule names are unique in a grammar

65. Rules can be either public or private

66. A public rule is visible outside the scope of the grammar document

67. A rule is private by default

68. An expansion describes a set of word sequences (sentences)‏Copyright © 2010 Nu Echo Inc.

69. Grammar RulesSyntax of a rule definition:public$name=expansion;orprivate$name = expansion;or$name = expansion;Copyright © 2010 Nu Echo Inc.

70. Rule namesA rule name must be a valid XML Name

71. http://www.w3.org/TR/2000/REC-xml-20001006#NT-Name

72. But:

73. Cannot be NULL, VOID, GARBAGE

74. Must not contain '.', ':', '-'

75. Rule names begin with '$'

76. Ex: $number $names $digitsCopyright © 2010 Nu Echo Inc.

77. Basic ExpansionsCopyright © 2010 Nu Echo Inc.

78. ExpansionsWords (aka tokens)‏

79. A string that the recognizer can convert to a phonetic representation

80. Typically a word in the specified language

81. Words are delimited by whitespaces, and$, <, >, (, ), /, |, [, ], {, }, !

82. Can be enclosed in “”Copyright © 2010 Nu Echo Inc.

83. ExpansionsWords (cont'd)‏

84. Examples:

85. hello

86. Montréal

87. trente-deux

88. “San Francisco”Copyright © 2010 Nu Echo Inc.

89. ExpansionsWords (cont'd)‏

90. Tips:

91. Avoid acronyms, like “IBM” (unless word is in the dictionary)Separate each letter with a “.” or “_”.

92. Good: “I.B.M.”, “I triple E”

93. Bad: “IBM”, “IEEE”

94. Don't use abbreviations.

95. Replace “Dr.” with “Doctor”, “St.” with “street"

96. Use spelled forms for numbers

97. Use “One hundred” instead of “100”Copyright © 2010 Nu Echo Inc.

98. ExpansionsSequences

99. Whitespace-separated expansions

100. Each expansion must match in turnEx: I would like to$day $month $yearCopyright © 2010 Nu Echo Inc.

101. ExpansionsChoices

102. To match one of a number of choices

103. Expansions separated by '|'Ex: one | two | three | four $yes | $no{answer = 'no'}Copyright © 2010 Nu Echo Inc.

104. ExpansionsGrouping

105. Parentheses group expansions (as do square brackets)

106. Enables encapsulation

107. Useful to ensure correct precedence in parsing a group of expansionsEx:no (it's | it is) not(oh | zero) { out = '0'}Copyright © 2010 Nu Echo Inc.

108. ExpansionsRule References

109. References to named expansions

110. Three types:

111. Local references

112. External references

113. Special rule namesCopyright © 2010 Nu Echo Inc.

114. ExpansionsLocal rule references

115. References to rules declared in the same documentEx:$date $civicNumber $digitCopyright © 2010 Nu Echo Inc.

116. ExpansionsExternal rule references

117. Implicit

118. Uses root rule

119. Root rule can be either public or private$<documentURI>Explicit

120. Rule must be declared public$<documentURI#ruleName>Media type can be specified:$<documentURI#ruleName>~<mediatype>Copyright © 2010 Nu Echo Inc.

121. ExpansionsExternal rule references (cont'd)‏Ex:$<../common/numbers.abnf>$<../common/numbers.abnf#oneToNine>$<http://localhost:8800/names.abnf?id=45>$<names.abnf?id=45>~<application/srgs+xml>Copyright © 2010 Nu Echo Inc.

122. ExpansionsSpecial rule references

123. $NULL

124. matches automatically

125. equivalent to ()‏

126. $VOID

127. matches nothing

128. $GARBAGE

129. matches anything

130. implementation-specific behaviorCopyright © 2010 Nu Echo Inc.

131. Advanced expansionsCopyright © 2010 Nu Echo Inc.

132. ExpansionsRepeats

133. Force the repetition of an expansion

134. Bounded: <n-m> or <n>

135. Unbounded: <n->Ex:$digit <7> | $digit <10>$topping <1->Copyright © 2010 Nu Echo Inc.

136. ExpansionsRepeats (cont'd)‏

137. Special case: [ E ]

138. Equivalent to E <0-1>

139. Or to ( E | $NULL )‏Ex:$hesitation = [euh] ok [euh];$date = $month [$year];Copyright © 2010 Nu Echo Inc.

140. ExpansionsRepeats (cont'd)‏

141. The probability of the repetition can be specified

142. Syntax: <n-m /prob/>

143. prob is value between 0.0 and 1.0Ex:$digit <2-4 /0.8/>$topping <1- /0.785/>Copyright © 2010 Nu Echo Inc.

144. ExpansionsChoices – Weighting‏

145. Multiplying factor attached to a choice

146. Positively biased when weight > 1.0

147. Negatively biased when weight < 1.0

148. Default weight is 1.0

149. Syntax: /n./ or /n.n/ or /.n/ or /n/Ex:(/1.7/ New York | /0.4/ Newark)‏Copyright © 2010 Nu Echo Inc.

150. ExpansionsLanguage

151. Overrides the default language

152. Applies to all words of the target expansion

153. Syntax: E!codeEx:yes | oui!fr-CA(Michel Tremblay|André Roy)!fr-CACopyright © 2010 Nu Echo Inc.

154. ExpansionsTags

155. To attach “meaning” to a sentence

156. Arbritrary strings enclosed in {}

157. Content depends on value of the tag-format headerEx: (two | second) {out.day = 1}$number{val = number.val}Copyright © 2010 Nu Echo Inc.

158. ExpansionsTags (cont'd)‏

159. Use {!{ ... }!} when tag must contain '}'.

160. Can appear as grammar header

161. must be followed by ';‘

162. Ideal for defining global functions or data structuresCopyright © 2010 Nu Echo Inc.

163. PrecedenceCopyright © 2010 Nu Echo Inc.