MULTILEVEL TAXONOMY BASED ON FEATURES DERIVED FROM TRAINING DOCUMENTS CLASSIFICATION USING FISHER VALUES AS DISCRIMINATION VALUES

A system, process, and article of manufacture for organizing a large text database into a hierarchy of topics and for maintaining this organization as documents are added and deleted and as the topic hierarchy changes. Given sample documents belonging to various nodes in the topic hierarchy, the tokens (terms, phrases, dates, or other usable feature in the document) that are most useful at each internal decision node for the purpose of routing new documents to the children of that node are automatically detected. Using feature terms, statistical models are constructed for each topic node. The models are used in an estimation technique to assign topic paths to new unlabeled documents. The hierarchical technique, in which feature terms can be very different at different nodes, leads to an efficient context-sensitive classification technique. The hierarchical technique can handle millions of documents and tens of thousands of topics. A resulting taxonomy and path enhanced retrieval system (TAPER) is used to generate context-dependent document indexing terms. The topic paths are used, in addition to keywords, for better focused searching and browsing of the text database.