Lifeworld Analysis

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 speci c example, we apply the tools to the analysis of the Toast system and show how versions of the system with very di erent control structures in fact implement a common control structure together with di erent conventions for encoding task state in the positions or states of objects in the environment.