This paper begins a process of building a semantic framework to link the many diverse interface notations that are used in more formal communities of HCI. The focus in this paper is on scenarios ­ single traces of user behaviour. These form a point of contact between approaches that embody very different models of interface abstractions or mechanisms. The paper looks first at discrete time models as these are more prevalent and finds that even here there are substantive issues to be addressed, especially concerning the different interpretation of timing that become apparent when you relate behaviour from different models/notations. Ubiquitous interaction, virtual reality and rich media all involve aspects of more continuous interaction and the relevant models are reviewed. Because of their closer match to the real world, they are found to differ less in terms of ontological features of behaviour.

keywords: scenarios, traces, dialogue models, temporal issues, formal methods in human-computer interaction, status-event analysis, ubiquitous interaction