Physigrams: modelling devices for natural interaction

This paper explores the formal specification of the physical behaviour of devices ‘unplugged’ from their digital effects. By doing this we seek to better understand the nature of physical interaction and the way this can be exploited to improve the design of hybrid devices with both physical and digital features. We use modified state transition networks of the physical behaviour, which we call physiograms, and link these to parallel diagrams of the digital state. These are used to describe a number of features of physical interaction exposed by previous work and relevant properties expressed using a formal semantics of the diagrams. As well as being an analytic tool, the physigrams have been used in a case study where product designers used and adapted them as part of the design process.