Abstract

An information retrieval system generates hierarchical query feedback to a user to facilitate the user in reformulating the query. The information retrieval system, which supports both text and theme queries, includes a knowledge base comprising a plurality of nodes of terminology, arranged hierarchically, that reflect associations among the terminology. For the hierarchical query feedback terms, the information retrieval system selects terminology that broadens and narrows the query terms by selecting parent nodes and child nodes, respectively, of the nodes for terminology that corresponds to the terms of the query. The information retrieval system also selects terminology that is generally related to the query terms by selecting nodes of the knowledge base that are cross linked to the nodes for terminology that corresponds to the terms of the query. Normalization processing, which generates canonical forms for query processing, and a content processing system, which generates themes for theme queries, are also disclosed.