In a data mining system, data is gathered into a data store using, e.g., a Web crawler. The data is classified into entities and stored into underlying vertical and horizontal tables respectively representing miner outputs and entities that can be the subjects of indexing. Data miners use rules to process the entities and append respective keys to the entities representing characteristics of the entities as derived from rules embodied in the miners, with the keys being associated with the entities in the tables. With these keys, characteristics of entities as defined by disparate expert authors of the data miners are identified for use in responding to complex data requests from customers.