TABLE OF CONTENTS The guidelines presented in this section are grouped in two primary classes: those that have to do with issues related to the uncertainty of recognition (Section 12.6.1), and those concerned with the circumstances guiding the selection of modalities (Section 12.6.2).
One essential aspect that has to be considered when building systems that rely on ambiguous interpretation is how uncertain interpretations are dealt with (Bourguet, 2006; Mankoff, Hudson, & Abowd, 2000). Shielding users from errors and providing graceful ways for handling unavoidable misinterpretations are essential usability concerns in this class of interfaces.
As discussed (Section 12.4.1), human language production involves a highly automatized set of skills not under users' full conscious control (Oviatt, 1996b). The most effective strategy for error avoidance is to design interfaces that leverage users' engrained cognitive and linguistic behavior in order to transparently guide input that avoids errors. In fact, training and practice in an effort to change engrained behavior patterns often prove useless (Oviatt et al., 2003, 2005). While this strategy can be the most effective, it is also the most demanding in terms of user modeling and implementation effort. In order to determine the root cause of errors and design an effective strategy for avoiding and resolving them, a cycle of experiments is required, as illustrated by the online case study (see Section 12.7). In this section, the effective principles of multimodal interaction are distilled as a set of guidelines.
