Relevance Sort

The search pass MUST retrieve all URLs that match the entire query. Afterward, however, it is necessary to decide how to order the results for presentation to the user. The system MUST support the TF/IDF scoring function, $s_{\mathrm{TF/IDF}}(d,q)$, which assigns a real-valued score to document $d$ with respect to query $q$ (see Appendix A for information on the TF/IDF scoring function). The system MUST sort results in decreasing order according to this scoring function before presentation to the user. The system MAY also offer an alternate scoring criterion, but if it does so it MUST offer some user interface mechanism (such as radio buttons) to allow the user to pick which scoring function to use.