15. A computer-readable storage device having instructions stored which, when executed on a computing device, cause the computing device to perform operations comprising: identifying segments of a dialog system based on a timing of probable user responses; exclusively activating a weighted grammar for a specific segment of dialog in the dialog system during the specific segment of the dialog, to yield an activated weighted grammar; and recognizing user speech received during the specific segment using the activated weighted grammar.
15. A computer-readable storage device having instructions stored which, when executed on a computing device, cause the computing device to perform operations comprising: identifying segments of a dialog system based on a timing of probable user responses; exclusively activating a weighted grammar for a specific segment of dialog in the dialog system during the specific segment of the dialog, to yield an activated weighted grammar; and recognizing user speech received during the specific segment using the activated weighted grammar. 18. The computer-readable storage device of claim 15 , wherein exclusively activating the weighted grammar further comprises a initiating a transition period blending a previously activated grammar and the weighted grammar to be activated.