Information-seeking tasks are usually characterized in terms of search and retrieval . In these tasks, users are seen to be looking for some items which are more or less loosely specified. An agent or system to aid such a task works by presenting items (or descriptions of items) to the user until the desired item is found. However, this is not the only possible task for users interacting with a large quantity of information. In particular, users encountering a new information space may simply wish to browse that space, to get a sense of what it might offer or what kinds of items could be retrieved in the course of a search.