Blind User Interfacing

There are specific usability requirements for developing dual interfaces, that is, graphical user interfaces that are also adapted for blind users. These include task adequacy, dimensional trade-off, behavior equivalence, semantic loss avoidance and device-independence. Consequently, the development of human-computer interfaces based on task, domain, dialog, presentation, platform and user models has to be modified to take into account these requirements. This paper presents the requirements for blind user interfacing, the changes to be made to the human-computer interface models and a framework that improves the development of dual user interfaces. The framework includes a set of guidelines for interface design, a toolkit for the low effort implementation of dual user interfaces, and a programming library for the inclusion of speech and Braille in applications. A case study of the development of one such dual interface application is also presented.