How would your favourite user model cope with these scenarios?

In a paper presented at the 1987 CHI conference (Young & Barnard, 1987), we proposed the use of scenarios as one methodological route to the development of user models of broader scope. In this article we summarise the argument and present five such scenarios as a challenge to the state of the art in user modelling. We invite the reader to ponder the question: How well would your favourite user modelling technique handle some, most, or all of these scenarios? And have you any further scenarios to add to those presented here?