Embodiments of the invention form an information set from the current set of index information available by the operations of the pre-search and runtime Search components of the search engine. A search request that contains search terms and/or other search criteria (e.g. date or file type) is entered by a user through an input interface. The search terms and the information set are worked through the search engine modules to provide the actual results sought by the user. These results are provided to the user via an output interface. Embodiments of a search engine involve runtime aspects that remove duplicate documents from the index, provide topical searching, and provide caching for the search engine.