1. A system for performing discovery of digital information in a subject area, comprising: an information collection maintained in a storage device; and a computer comprising a processor and memory within which code for execution by the processor is stored, comprising: a user interface of the computer configured to designate each of topics in a subject area, training material for the topics, and a corpus comprising electronically-stored digital information; a topic modeler configured to build candidate topic models on the computer, comprising: a seed word selector configured to select seed words for each of the topics, and a pattern generator configured to generate patterns from the seed words for each topic as candidate topic models for that topic; an index trainer to evaluate the topic models against the training material comprising: a pattern tester configured to match the patterns in each candidate topic model to the training material and to rate the candidate topic model based on topical prediction; and an index builder configured to build an evergreen index comprising topic models for each of the topics by pairing each topic to the candidate topic model that was best rated.