The defined grammar for the application plays heavily in the user's dialogue experience. The grammar definition, along with the prompt selection, provides the basis for the voice user interface.
Grammars should be defined in such a way that grammar match points are as distinct as possible. Grammar match points within close proximity of each other, such as "Dawn" and "Don," may map to the same phrase, thus skewing recognition rates. Supporting multiple active grammars adds ambiguity in the recognition. When more than one grammar is active simultaneously, as little overlap as possible should exist between the distinct grammars. This is necessary because most recognizer engines cannot determine the context within which the grammar phrases occur and will return the first match from a list of possibilities.