Interaction, interfaces and design

Many planning problems cannot be formulated in such a manner t h a t a well developed optimizing technique can be applied to them to arrive at a satisfactory solution. This may be because of the structure of the problem itself, it may be because objectives and even parameters cannot be adequately described or it may be due to the need to include subjective factors. Additionally there is a class of problems for which the cost of the computation required to reach an optimum is not warranted by the expected gains. When we examine the tools available to a problem solver who wishes to use interactive computing, we find that the languages currently used to achieve interaction are both clumsy and restrictive.