Making graph-based diagrams work in sound: the role of annotation

Nonlinear forms of diagrammatic presentation, such as node-arc graphs, are a powerful and elegant means of visual information presentation. Although providing nonvisual access is now routine for many forms of linear information, it becomes more difficult as the structure of the information becomes increasingly nonlinear. An understanding of the ways in which graphs benefit sighted people, based on experiments and the literature, together with the difficulties encountered when exploring graphs nonvisually, helps form a solution for nonvisual access to graphs. This article proposes that differing types of annotation offer a powerful and flexible technique for transferring the benefits of graph-based diagrams, as well as for reducing disorientation while moving around the graph and for tackling some of the inherent disadvantages of using sound. Different forms of annotation that may address these problems are explored, classified, and evaluated, including notes designed to summarise and to aid node differentiation. Graph annotation may be performed automatically, creating a graph that evaluation shows requires less mental effort to explore and on which tasks can be achieved more effectively and more efficiently. Copyright © 2013 Taylor & Francis Group, LLC.