An improved information retrieval system user interface for retrieving information from a plurality of sources and for storing information source descriptions in a knowledge base. The user interface includes a hypertext browser and a knowledge base browser/editor. The hypertext browser allows a user to browse an unstructured information space through the use of interactive hypertext links. The knowledge base browser/editor displays a directed graph representing a generalization taxonomy of the knowledge base, with the nodes representing concepts and edges representing relationships between concepts. The system allows users to store information source descriptions in the knowledge base via graphical pointing means. By dragging an iconic representation of an information source from the hypertext browser to a node in the directed graph, the system will store an information source description object in the knowledge base. The knowledge base browser/editor is also used to browse the information source descriptions previously stored in the knowledge base. The result of such browsing is an interactive list of information source descriptions which may be used to retrieve documents into the hypertext browser. The system also allows for querying a structured information source and using query results to focus the hypertext browser on the most relevant unstructured data sources.