Multimodal user interface (MUI) allows users to interact with a computer system through multiple human- computer communication channels or modalities. Users have the freedom to choose one or more modalities at the same time. MUI is especially important in mobile devices due to the limited display and keyboard size. In this chapter, we provide a survey of the MUI design in mobile technology with a speech-centric view based on our research and experience in this area (e.g., MapPointS and MiPad). In the context of several carefully chosen case studies, we discuss the main issues related to the speechcentric MUI in mobile devices, current solutions, and future directions.
Key Terms in this Chapter
User-Centered Design: A design philosophy and process in which great attention is given to the needs, expectations, and limitations of the end user of a human-computer interface at each stage of the design process. In the user-centered design process, designers not only analyze and foresee how users are likely to use an interface, but also test their assumptions with actual users under real usage scenario.
Modality: A communication channel between human and computer, such as vision, speech, keyboard, pen, and touch.
Speech-Centric Multimodal User Interface: A multimodal user interface where speech is the central and primary interaction modality.
Typed feature Structure: An extended, recursive version of attribute-value type data structures, where a value can, in turn, be a feature structure. It indicates the kind of entity it represents with a type, and the values with an associated collection of feature-value or attribute-value pairs. In the typed feature structure, a value may be nil, a variable, an atom, or another typed feature structure.
Modality Fusion: A process of combining information from different input modalities in a principled way. Typical fusion approaches include early fusion, in which signals are integrated at the feature level, and late fusion, in which information is integrated at the semantic level.
Multimodal User Interface: A user interface with which users can choose to interact with a system through one of the supported modalities, or multiple modalities simultaneously, based on the usage environment or preference. Multimodal user interface can increase the usability because the strength of one modality often compensates for the weaknesses of another.
Push to Talk: A method of modality switching where a momentary button is used to activate and deactivate the speech recognition engine.