Merging XML Indices

Using separate indices for each element and merging their results has proven to be a feasible way of performing XML element retrieval; however, there has been little work on evaluating how the main method parameters affect the results. We study the effect of using different weighting models for computing rankings at the single index level and using different merging techniques for combining such rankings. Our main findings are that (i) there are large variations on retrieval effectiveness when choosing different techniques for weighting and merging, with performance gains up to 102%, and (ii) although there does not seem to be any best weighting model, some merging schemes perform clearly better than others.