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The justified user model: a viewable, explained user model*

R Cook and J Kay ?
Basser Department of Computer Science University of Sydney
[email protected],[email protected]


This paper describes our experiences with giving users access to the system's model of them. This access is supported by a number of tools that enable a user to see various forms of information: an overview display serves as a navigation tool as well as a helpful summary; the main model viewer program enables the user to see the detailed model the system holds; the justification part explains the system's reasoning about the user model; the explanation subsystem provides a tailorable glossary of the terms used in the user model description; and the change facility allows the user to add their view of the correct value of components of the model. We outline the series of studies we have conducted to learn how users respond to our visual displays of a user model. These indicate a new purpose for a user model as a useful communication tool that enables users to find information that interests them as well as to communicate the way that they would like to be modelled.
We also discuss some issues that arise from making the user model accessible. These affect the way that the programmer sees their relationship to the user. They also highlight the need to address different interpretations of a user model.


The user model is becoming increasingly important in a number of classes of systems that are currently of considerable interest: customised documentation, teaching systems, information filtering and other tailored interfaces.
There are many potential benefits from making a


* This work is supported by Telecom Australia Grant Reference Y05/04/34 and BLO/02/02/89

? R Cook is currently at Message Handling Systems, Newtown, Australia To appear UM94, 4th User Modeling Conference, Cape Code, USA>

user model accessible to the user it describes. This is on the grounds of the user's right to access information about themselves, the accountability it enforces on the programmer creating and using the user model and the benefit of having the user verify or correct the information in the user model. In addition, there appear to be educational benefits (Crawford and Kay 1992, Crawford and Kay 1993). Others have argued the importance of making complex systems more comprehensible (for example, Fisher 1991; Maass 1983). This paper describes viewer programs that enable the user to see their user model, expressed in the um representation (Kay 1990). From the very first, um was designed to make the user model accessible to the user. The viewers described here enhance practical accessibility because they make it far easier to browse through the model and to appreciate its overall structure and values.
Our development of the accessible user model and associated viewer programs has been in the context of a number of projects. Our most extensive work has involved systems that support learning of the sam text editor (Pike, 1987). The primary goal in this work has been to enable users to become more effective sam users. We have created several coaching systems, each based on a different approach to teaching about sam (ParandehGheibi and Kay 1993). Another series of coaching experiments have taught users about Unix (Butler, 1992). We have also been studying various models of usage and learning of sam (Benyon, Kay and Thomas 1992). We have become particularly interested in the way that a viewable user model can, itself, be a useful tool. So, for example, one of our sam coaching systems allowed users access to the viewer programs. We expected that such access would enable these users to approach their learning about sam differently.