1. A method for generating a set of rules used to provide preliminary rankings to documents, the method comprising: analyzing a final ranking function used to calculate final rankings for a plurality of documents; from the final ranking function, identifying potential preliminary ranking features that include one or more static ranking features that are query independent and one or more dynamic atom-isolated components that are related to a single atom; selecting from the potential preliminary ranking features one or more preliminary ranking features to use for a preliminary ranking function; and using at least the one or more preliminary ranking features to generate a set of rules that is used to provide a preliminary ranking for the plurality of documents.