The viability of providing adaptive user interfaces has been demonstrated ([3], [5]). Such systems identify differences between users in order to provide purposeful change at the user interface. Thus, adaptive systems have objectives, as indicated by the term 'purposeful.' The research reported here takes an important step forward by demonstrating that adaptive systems can be built that regulate their own behaviour by assessing whether their adaptations are being successful in meeting these objectives.

The design and implementation of adaptive systems as opposed to non-adaptive systems creates new demands on user interface designers. This paper discusses a few of these demands as encountered by the authors while utilising a formal notation for the design of an adaptive user interface to an electronic mail system. Recommendations for the extension of this formal notation are proposed and discussed.