Making systems sensitive to the user's changing resource limitations

Situationally determined limitations in users' "resources" (e.g. time and working memory) constitute an increasingly important challenge to adaptive interfaces--one which does not yield easily to straightforward solutions. This article gives an overview of a research program that emphasizes empirically based understanding of this problem and the use of an explicit model of the relevant causal relationships. After introducing the challenge and comparing several possible approaches to it, we summarize related work on adaptive systems and the empirical research that forms the basis of the Ready prototype. The structure and workings of this prototype are discussed and illustrated with examples. We conclude by summarizing how the results obtained so far can form the basis for practically applied systems. (C) 1999 Elsevier Science B.V. All rights reserved.