Philip Agre pagre@ucsd.edu
Department of Communication 0503
University of California, San Diego
La Jolla, CA 92093, USA
and
Ian Horswill ian@ils.nwu.edu
Northwestern University Computer Science Department
1890 Maple Avenue
Evanston, IL 60201, USA
We argue that the analysis of agent/environment interactions should be extended to include the conventions and invariants maintained by agents throughout their activity. We refer to this thicker notion of environment as a lifeworld and present a partial set of formal tools for describing structures of lifeworlds and the ways in which they computationally simplify activity. As one specific example, we apply the tools to the analysis of the TOAST system and show how versions of the system with very different control structures in fact implement a common control structure together with different conventions for encoding task state in the positions or states of objects in the environment.