Formal models for user-interface design are important because formality provides a number of advantages, such as early use in the design process, precise prediction of usability aspects, precision for design and communication, and enabling automatic generation of user interfaces.
Within the domain of formal models, the thesis attempts to answer two main questions:
(1) what is a good formal specification model for user-interface design?
(2) what is a good method for user-interface design, based on such a model?
To answer the first question, a number of criteria are developed for evaluating the available formal models such as ETIT, TAG, CLG, GOMS, and ETAG. Mainly on the basis of the completeness of the conceptual specification and the psychological validity, ETAG (Extended Task-Action Grammar) is selected for further development. Specifically aimed at validating the notation, the thesis discusses the psychological basis and it provides a manual for creating the representations.
The second question is answered from a radical user-centered perspective: the user interface is defined as everything a user must know in order to perform tasks, software design is treated as subordinate to user interface design. ETAG-based User Interface Design follows the common scheme for user interface design, except that ETAG is used as the main representation method, and iteration between design stages is avoided as much as possible. Aimed at validating both the notation and the design method, the thesis discusses task-analysis, user-interface analysis, and the generation of help information and user interface prototypes.
The main conclusions from the study are as follows. ETAG and ETAG-based User Interface Design perform very well. There are two main areas for further development. To address the relevance of perceptual information to task performance, methods and tools are required to describe and analyse the perceptual interface. To address the relevance of the dynamical aspects of the interaction to task performance, such as learning, it is necessary to bridge the gap between static knowledge models, like ETAG, and dynamic knowledge models, like SOAR.
For a brief overview about ETAG, the topic of this thesis, see: Everything you always wanted to know about ETAG ... -