53 Copyright © 2010, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 3 A Formal Approach to the Verifcation of Adaptability Properties for Mobile Multimodal User Interfaces Nadjet Kamel University of Moncton, Canada Sid Ahmed Selouani University of Moncton, Canada Habib Hamam University of Moncton, Canada INTRODUCTION The development of new interactive devices and technologies such as speech recognition, visual recognition and gesture recognition enriches User Interfaces (UIs) interactions and allows user to interact with systems in a more natural way. Mul- timodal User Interfaces (MUIs) are characterized by several possibilities, defined as modalities, to interact with the systems. The users can choose AbsTRACT Multimodal User Interfaces (MUIs) offer to users the possibility to interact with systems using one or more modalities. In the context of mobile systems, this will increase the fexibility of interaction and will give the choice to use the most appropriate modality. These interfaces must satisfy usability properties to guarantee that users do not reject them. Within this context, we show the benefts of using formal methods for the specifcation and verifcation of multimodal user interfaces (MUIs) for mobile systems. We focus on the usability properties and specifcally on the adaptability property. We show how tran- sition systems can be used to model the MUI and temporal logics to specify usability properties. The verifcation is performed by using fully automatic model-checking technique. This technique allows the verifcation at earlier stages of the development life cycle which decreases the high costs involved by the maintenance of such systems. DOI: 10.4018/978-1-60566-978-6.ch003