MAS.632 Conversational Computer Systems - MIT OpenCourseWare

178 VOICE COMMUNICATION WITH COMPUTERS
SUMMARY
variety of voice interfaces. Subsequent projects, most notably Conversational
Desktop (described in Chapter 12), focused on the parsing and error management
techniques initiated with Put That There.
This chapter discussed incorporating speech recognition into interactive applications.
There are many approaches to recognition, and different classes of speech
recognizers are amenable to varying styles of applications. Recognition may be
employed when no other input channel is available, as an adjunct to existing
input channels (keyboard and mouse), or as a direct substitute for the keyboard
for text entry. Each of these application areas has different recognition requirements
and derives unique benefits from the use of voice input.
Poor recognition accuracy is the dominant concern in designing interaction
techniques to employ speech input. Insertion, rejection, and substitution errors
all degrade performance but in different ways. Errors can be minimized by careful
choice of vocabulary and microphone placement and by chosing cooperative
subjects, but these factors may not apply to real-world deployment of recognition
technology. As recognition accuracy improves, errors inevitably occur and can be
managed through user participation in a variety of confirmation and repair
strategies; however, it must be stressed that some interaction techniques will
always be required to ensure accurate communication. This chapter discussed
the use oflanguage and task constraints in the automatic detection of recognition
errors; we will return to the topics of language understanding and dialogue structure
in Chapter 9.
This chapter's discussion of error recovery implies that developing recognitionbased
applications is much more demanding than simply adding a new input
device to existing applications. Xspeak was offered as an example of a meta-application,
controlling the window system, and thereby selecting an application to
receive keyboard events rather than modifying the applications themselves. Put
That There was described as an example of simple parsing techniques and spoken
dialogue with the user to resolve ambiguities. Although Xspeak illustrates an
attempt to closely match the specific assets of speech recognition to the range of
tasks performed at the workstation, the experience of its users also demonstrate
the frustrations associated with using recognition in daily work.