Short Term Memory for Speech Based Input

nWIMP based GUIs avoid short term memory requirements by continuously presenting a discrete set of allowed input choices. nHowever for speech based interfaces to benefit from their inherent expressiveness, memory is relied upon to recall the set of allowed input commands. nThus speech based interfaces often need to provide a guidance system similar to those presented by GUIs (i.e. “What can I say?”), as an initial training mode.  The guidance system also help to establish the actual vocabulary available to the user.