In this paper we describe a method for IS design which focus on constructing the social reality in which the IS is used. This reality is structured as a particular form of work practice – the activity domain – which is the main construct in the Activity Domain Theory. The gist of this theory is to integrate coordinating elements of a practice into a coherent whole in which the IS is one of these elements.The theory originated in the Ericsson telecommunication company where it has been gradually refinedover more than a decade by the author. It has profoundly influenced the coordination of the development of the 3^rd generation of mobile systems