Designing the user interface for multimodal speech and pen-based gesture applications: state-of-the-art systems and future research directions.
Sharon Oviatt and Phil Cohen and Lizhong Wu and John Vergo and Lisbeth Duncan and Bernhard Suh

Usability is the measure of the quality of a user's experience when interacting with a product or system. According to ISO 9126 software standards this quality characteristic is composed of three subcategories: understandability, learnability, operability. In this context, it is concerned with methods for evaluating the usability of Language Technology systems for end users in typical contexts.