Ubiquitous interaction places the user in the centre of dynamic configurations of technology, where work not necessarily is performed through a single personal computer, but supported by a multiplicity of technologies and physical devices. This paper presents an activity-theoretically based framework for analyzing
, i.e. a set of mediators that are or can be continuously substituted with the purpose of highlighting expected and indented uses, and the conflicts encountered when attempting substitution between them. The paper develops a four-leveled analysis of such mediators, and point towards a minimalist approach to design of ubiquitous interaction.