1. A computer-implemented method for processing documents in a document database using a computer-implemented system comprising a processor and a display operatively coupled to the processor, the method comprising: operating the processor to perform the following generating an initial ranking of retrieved documents using an information retrieval system and based upon a user search query provided by a user; displaying for the user the initial ranking of the retrieved documents; permitting user selection of a plurality of vocabulary words based upon occurrences thereof in at least some of the retrieved documents; generating respective relevancies of the user-selected vocabulary words in the retrieved documents; generating a re-ranking of the retrieved documents based on the generated respective relevancies of the vocabulary words; selecting N top ranked documents from the retrieved documents before processing the plurality of vocabulary words, with N being an integer greater than 1; and wherein generating the respective relevancies and generating the re-ranking are with respect to the N top-ranked documents; and operating the display to display for the user the re-ranking of the documents, and for each document being displayed, also to display its initial ranking.