Blind User Interfacing: Requirements, Models and a Framework

Blind User Interfacing: Requirements, Models and a Framework

Fernando Alonso (Technical University of Madrid, Spain), José Fuertes (Technical University of Madrid, Spain), Ángel González (Technical University of Madrid, Spain) and Loïc Martínez (Technical University of Madrid, Spain)
DOI: 10.4018/978-1-61350-456-7.ch110
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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.
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The development of user interfaces for blind people has taken two complementary research and development paths: (1) adapting existing visual interfaces for blind users and (2) building dual interfaces or interfaces especially adapted for blind or visually impaired users.

The adaptation of visual interfaces for blind people emerged in response to the need to adapt the directly manipulated graphical environments that were proliferating to enable people with impaired vision to use common development software. The pioneering projects on this subject include OutSpoken (Edwards, 1991) and Mercator (Mynatt and Edwards, 1992a), which aimed to adapt MacOS and X-Windows, the most commonly used graphical environments in the early 90s. These projects encouraged the development of the Off Screen Model (Mynatt and Edwards, 1992b), the adaptation model on which most of the tools available for adapting interfaces for blind users are based. Tools like Orca help provide access to applications and toolkits that support the AT-SPI (e.g., the GNOME desktop) (GNOME, 2009), VoiceOver gives blind people access to MacOS X systems (Apple, 2009), and using Hal Screen Reader (Dolphin Computer Access, 2009), JAWS (Freedom Scientific BLV Group, 2008) and Window-Eyes (GW Micro, 2009) non-sighted users can access Windows environments.

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