Very different to the design of DM interfaces
Interface must taken on a more sophisticated conversational
style
Since speech is slow, feedback must balance sufficiency
with brevity
Error detection difficult (text returned is best
guess)
Error correction often means changing modalities
and modifying recognition model
Users give vital clues regarding potential dialog
between user and computer
Standard usability evaluation methods can be difficult:
User cannot ask questions of facilitator
Verbal protocol cannot be used
"Wizard of Oz" approach used to test and
refine design