Phone_Number.gram
This example ABNF grammar recognizes a spoken North American phone number — an optional area code followed by a seven-digit number — and uses semantic interpretation to return a structured result with two string members, areacode and number. When the caller does not speak an area code, it defaults to 858. The grammar demonstrates several common techniques: mapping spoken digit words to their numeric values, using the repeat operator to require a fixed number of digits, and building a structured semantic result with the out variable.
Example
| #ABNF 1.0; mode voice; language en-US; tag-format <semantics/1.0>; root $PhoneNumber; $Digit = (ONE {out = "1"} | TWO {out = "2"} | THREE {out = "3"} | FOUR {out = "4"} | FIVE {out = "5"} | SIX {out = "6"} | SEVEN {out = "7"} | EIGHT {out = "8"} | NINE {out = "9"} | (ZERO | O) {out = "0"} ); /* * $AreaCode resolves to a three digit string * after semantic interpretation. */ $AreaCode = { out = "" } ( $Digit { out += rules.Digit } ) <3>; /* * $Number resolves to a seven digit string * after semantic interpretation. */ $Number = { out = "" } ( $Digit { out += rules.latest() } ) <7>; /* * After semantic interpretation, * $PhoneNumber resolves to a structure with two member variable strings, * areacode (which defaults to "858"), and number. */ $PhoneNumber = ( [AREA CODE | ONE] $AreaCode { out.areacode = rules.latest() } $Number { out.number = rules.latest() } ) | ( $Number ) { out.areacode = "858"; out.number = rules.latest() }; |