Criteria and technique to choose a good ρ parameter for the D-index

D-index is among the most efficient similarity search indexes, its performance dramatically depends on the choice of the ρ parameter. Although the importance of this parameter, there are no techniques or criteria proposed to choose an adequate ρ value. In this paper, we propose a criteria and a technique that ensure a good choice of ρ, and we use this technique to modify the original D-index to make it able to choose an adequate value of ρ. The experiments show that the modified D-index is more efficient when the exclusion set is small and the comparison between original and modified D-index proves that the modified D-index presents a good improvement in terms of the search cost.