PLUMB: An Interface for Users Who are Blind to Display, Create, and Modify Graphs
Matt Calder, Robert F. Cohen, Jessica Lanzoni, Yun Xu · 2006 · Proceedings of the 8th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '06) · doi:10.1145/1168987.1169046
Summary
This demonstration paper presents the latest version of PLUMB (exPLoring graphs at UMB), extending it beyond passive graph exploration to include the ability for blind and sighted users to create and modify graphs. The original PLUMB system displayed drawn graphs on a Tablet PC and used audio cues to help blind users navigate them via a stylus. This new version adds two key capabilities. First, a keyboard-based navigation interface complements the pen-based approach — inspired by observing how fast blind users navigate the web, keyboard bindings allow users to quickly get information about edges and vertices and navigate through the graph without the precision demands of pen-based tracing, though at the cost of some distance and geographic relationship information. Users can also perform auto-complete searches to jump directly to named vertices. Second, PLUMB now functions as a graph editor, allowing both sighted and blind users to add, remove, and modify graph elements using either graphical editing tools or a command line interface. Graph data is stored in GXL (an XML-based format), so documents can be easily opened and explored. The system is designed to be usable by both blind and sighted users, with the interface appealing to different navigatory senses that complement each other for optimal graph understanding.
Key findings
The paper demonstrates several educational applications built with PLUMB. Constellation drawings have been rendered so students can trace and understand star pattern shapes using the pen-based mode. Molecular diagrams (similar to the Kekule project) allow chemistry students to explore molecular structures through audio-tactile interaction. Train maps have been implemented to allow students to explore routes and trip options using the keyboard-based system. A knowledge mapping (concept/mind mapping) prototype has been developed, where users build diagrams showing relationships between research concepts — an application shown to be effective for improving critical thinking and writing skills. The dual-interface approach (pen for spatial/geographic understanding, keyboard for rapid structural navigation) recognises that different tasks and user preferences benefit from different interaction modalities. The command line interface for graph editing makes creation accessible without requiring precise spatial manipulation.
Relevance
This paper extends the PLUMB system from a consumption tool to a creation tool, addressing an important gap: blind users should not only be able to read graphs and diagrams but also create and modify them independently. The dual pen/keyboard interface is a practical design decision that acknowledges the trade-offs between spatial understanding (pen) and efficient navigation (keyboard). The educational applications — constellations, molecular diagrams, train maps, and concept mapping — demonstrate the breadth of domains where graph accessibility matters beyond computer science. The knowledge mapping application is particularly noteworthy, as concept mapping and visual brainstorming tools are widely used in education and professional settings but are typically entirely visual. By making these tools accessible, PLUMB supports equal participation in collaborative and educational activities that depend on relational thinking and visual organisation of ideas.
Tags: visual impairment · graph accessibility · sonification · audio interface · tablet PC · education · non-visual interaction · knowledge mapping
Standards referenced: GXL (Graph eXchange Language)