This preface tells the story of how Multimodal Usability responds to a special challenge. Chapter 1 describes the goals and structure of this book.

The idea of describing how to make multimodal computer systems usable arose in the European Network of Excellence SIMILAR – “Taskforce for creating human-machine interfaces SIMILAR to human-human communication”, 2003– 2007, www.similar.cc. SIMILAR brought together people from multimodal signal processing and usability with the aim of creating enabling technologies for new kinds of multimodal systems and demonstrating results in research prototypes.Most of our colleagues in the network were, in fact, busy extracting features and figuring out how to demonstrate progress in working interactive systems, while claiming not to have too much of a notion of usability in system development and evaluation. It was proposed that the authors support the usability of the many multimodal prototypes underway by researching and presenting a methodology for building usable multimodal systems.

We accepted the challenge, first and foremost, no doubt, because the formidable team spirit in SIMILAR could make people accept outrageous things. Second, having worked for nearly two decades on making multimodal systems usable, we were curious – curious at the opportunity to try to understand what happens to traditional usability work, that is, work in human–computer interaction centred around traditional graphical user interfaces (GUIs), when systems become as multimodal and as advanced in other ways as those we build in research today. Third, we were perhaps ready for a stab at making usability and human–system interaction intelligible to newcomers, having often wondered why this field seems so hard to some, including many graduate students and PhD students in computer science and engineering. Finally, of course, we grossly underestimated the effort required for trying to make sense of multimodal usability.

This book is about how to develop and evaluate multimodal systems which are usable by, or fit, people. The main objective is to answer the practical question of what system developers need to know and be able to do in order to develop usable new multimodal applications. The need to know is addressed in the first part of the book, in which the role of development and evaluation for multimodal usability in the software engineering life-cycle is described, and 9 key multimodal usability parameters are presented as well as theory of modalities and multimodality. The need to be able to do is addressed in the second part of the book. The distinction between interleaved and iteratively performed (i) development for multimodal usability and (ii) evaluation for usability is discussed.