Mobile users generate a number of new problems by changing the context of interaction with the system. While context has always been relevant to interaction, the fact this can change, and the fact that tasks may be dependant on these contexts adds a new dimension to the design problem. Furthermore in some cases applications should be able to adapt to be pertinent to the current context, adding to the complexity of the applications to be constructed. With regard to “ambient” interaction, where systems are attempting to intelligently and unobtrusively help the user, understanding the user's intentions and providing relevant and adequate responses is a new problem. Furthermore, supporting the construction of such applications provides an additional challenge.