For experienced users, cues are rendered so that at any time {HEAD ~ the user} can say {TAIL ~ a desired keyword} to invoke the corresponding application 
say
For experienced users , cues are rendered so that at any time { HEAD ~ the user } can say { TAIL ~ a desired keyword } to invoke the corresponding application
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH