The goal of system design is to support users in the activities they wish to undertake. Using an interactive system is a human activity: we need to make sure that usage is consistent with the user's physical and cognitive abilities and the social environment they inhabit. It is important not to think of human activity as planned or programmed in the same sense as the steps performed by a computer [8]. Many things which people do are in response to their immediate environment --- they are reactive rather than active.
In designing a text retrieval system, we are creating a tool for finding sources of information about a topic, which must compete with those already available. If it is seen as inferior, it will not be used; if it enables tasks to be performed better or more quickly it may be adopted in preference to the other available tools. With information retrieval systems in general, users wish to:
The ENQUIRE system was designed to address only the first of these needs, although it was acknowledged that in practice information about item availability is a powerful incentive for potential users. The intention was to extend users' ability to find items of interest by supporting them in interactive query formulation and re-formulation.