Grammar support is formalized with VoiceXML 2.0. This Specification provides support for built-in grammars and explicit grammars. We introduced built-in grammars in 2.1.4, “Grammars: mapping a user response to a value,” on page 31. Explicit grammars can be written inline or referenced externally.
VoiceXML 2.0 states that an interpreter should support at least one of the following three grammar standards:
XML form of the W3C Speech Recognition Grammar Format (GRXML),
Augmented BNF (ABNF) form of the W3C Speech Recognition Grammar Format,
Java Speech Grammar Format (JSGF).
Note that the first two grammars, GRXML and ABNF, are both developed by the W3C and are completely compatible and transformable to one another format. We will use ...