Utterance-Based Systems: Organization and Design of AAC Interfaces
Timothy J. Walsh · 2010 · Proceedings of the 12th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS 2010) · doi:10.1145/1878803.1878895
Summary
This paper describes the design and development of an utterance-based AAC interface for literate, high-functioning adults who need communication support in public situations such as restaurants or shops. The central design challenge in AAC interfaces is balancing message accuracy with communication speed — users need to convey precise meaning quickly enough to maintain conversational flow. Utterance-based systems address this through a three-phase model: preparing prestored text that users would anticipate needing, organising this text via a hierarchical schema-based structure that mirrors real-world event sequences, and providing an interface for quick access and editing of messages. The research proceeded in three stages: analysing existing AAC interfaces (particularly the DynaVox Series5 with InterAACT software) and deriving user requirements; designing an interface based on four fundamental principles drawn from Don Norman's design theory (consistency, logical GUI, uniform functionality, and intuitive information organisation); and implementing the design first as a Python/PyGame prototype for rapid feedback, then as a full Java implementation with XML-tagged prestored messages. The schema-driven organisation maps interface navigation to real-world event sequences — for example, a restaurant schema would present greetings, then ordering, then payment — so the user progresses through the interface as the real situation unfolds.
Key findings
The interface design centres on four principles derived from Norman's "Seven Principles for Transforming Difficult Tasks into Simple Ones": consistent layout (navigation panel and display window always in the same location), logical graphical interface, uniform functionality (distinct button shapes always perform the same type of action), and intuitive schema-based information organisation. The consistent and always-visible navigation panel and message display window serve as familiar anchors while dynamic content changes around them. Uniform functionality — where, for example, circular buttons always perform one type of action and square buttons another — was found to be critical; prior research showed that AAC interfaces without uniform functionality became confusing because users could not predict outcomes. The schema-based organisation reduces search time by presenting only messages relevant to the current stage of an interaction, drawing on the same mental models users already have of familiar events. The prototype gathered feedback from speech pathologists, AAC users, and interface design researchers, with a full Java implementation and formal user evaluation planned.
Relevance
This paper provides a practical design framework for AAC interfaces that is grounded in both cognitive science (schema theory from Schank and Abelson) and established HCI principles (Norman's design guidelines). For accessibility practitioners, the key insights are broadly applicable beyond AAC: the importance of uniform functionality where identical visual elements always behave identically; the value of organising information to match users' mental models of real-world sequences rather than arbitrary categories; and the critical trade-off between accuracy and speed in communication interfaces. The schema-based approach — where the interface mirrors the progression of a real-world event — is a compelling model for any system where users need to find information quickly under time pressure. The work also demonstrates the value of analysing existing commercial products (DynaVox) to derive requirements before designing new interfaces. The paper is limited by not yet having formal evaluation results, but the design principles are well-founded and the iterative prototyping approach (Python rapid prototype followed by full Java implementation) is sound.
Tags: augmentative and alternative communication · interface design · utterance-based system · communication rate · assistive technology · speech generation