An Assumption-based Truth Maintenance System in Active Aid for UNIX Users

This paper deals with the problem of assigning meaning to the interaction of a user with a command-driven system such as UNIX. This research is part of the construction of an active intelligent help system that monitors users in order to offer spontaneous help when they are facing problems. In order to ensure this, the help system must build and maintain a model of the user. We describe a mechanism that is used by the user modelling component of such a help system. This mechanism makes explicit assumptions about the user which account for different hypotheses about what the user is actually thinking at every stage of the interaction. The consistency of these assumptions is managed by an Assumption-based Truth Maintenance System (ATMS). The selection between a number of different user models is based on the information which is extracted from the feedback that UNIX provides in response to user actions. This revised version was published online in August 2006 with corrections to the Cover Date.