On relevance weights with little relevance information

The relationsh~p between the Robertson/Sptxck Jones relevancxi mighting formula and the Croft/Harper version for no relevanee information is d~ussed. A method of avoiding the negative weighta sometimes implied by the Cr&/Harper version is propowx which turna out to involve a return to the original Sparck Jones inverse collection frequency weight. The paper then goes on to propose a new way of using small amounts of relevanee information in the e9tim* tion of relevance weiglh Some experiments using TREC data are reported.