Incidentally, if you want to see why the weighting schemes work like this, consider the case of a database with two documents, one of which contains all the text from the first twice. You probably want to give these similar weight - certainly the doubled document shouldn't get twice the weight for most applications. For BM25 you can adjust a parameter to tune how much influence the document length has. If you're happy using QueryParser, just apply the above to the Query object it produces (i.e. query in the above code snippet comes from QueryParser). Cheers, Olly