Optimum query Seeks to find a query that maximizes similarity to elevant documents while minimizing similarity with non-relevant documentsLet CrC_rCr denote set of relevant docs, Let CnrC_{nr} Cnr denote set of non-relevant docs.qopt=arg maxp[sim(q,Cr)−sim(q,Crn)]q_{opt} = \argmax_p [sim(q, C_r) - sim(q, C_{rn})]qopt=argmaxp[sim(q,Cr)−sim(q,Crn)]qopt=∑d∈Crdi∣Cr∣−∑d∈Crndi∣Crn∣q_{opt} = \frac{\sum_{d\in C_r} d_i}{|C_r|} - \frac{\sum_{d\in C_{rn}} d_i}{|C_{rn}|}qopt=∣Cr∣∑d∈Crdi−∣Crn∣∑d∈Crndi