The design and re-design of a simultaneous representation of conceptual and device models

This paper reports on the design and re-design of an Ontological Sketch Model. OSM is a representation and method of usability assessment that is based on descriptions of the device model and the user’s conceptual model of that device. The ultimate aim of this work is to develop an approach that focuses attention on device and conceptual models, and that is usable, useful and widely available for use. We present the rationale for the design of the OSM. The initial design for the OSM was based on descriptions of the entities in the domain of application, actions that the user can perform, and relationships (such as “constrains” and “affects”) between entities. A formative evaluation of the usefulness and usability of this design showed that the approach was promising, but also highlighted limitations of the representation. In particular, novice analysts had difficulty writing descriptions at an appropriate level of detail and understanding the meanings of some relationships. This led to a re-design of the notation. The re-design is still based on descriptions of entities, actions and relationships, but provides stronger constraints on what can be expressed, reducing the possibility of novices producing inappropriate descriptions and also providing a better basis for formalising usability properties. We have also placed greater emphasis on formalising the fit or misfit between device and conceptual models.