1. A method for selecting a preferred data set, comprising: generating, by one or more processors, a candidate data set based on a first data set having a first join attribute, a first aggregate attribute and a first local attribute, and a second data set having a second join attribute compatible with the first join attribute and a second aggregate attribute, wherein the candidate data set includes a total attribute having a value that is based on aggregating a value associated with the first aggregate attribute and a value associated with the second aggregate attribute, and the candidate data set further includes the first local attribute selected from the first data set; and selecting, by one or more processors, the preferred data set from the candidate data set based on the total attribute and the first local attribute, wherein no tuple in the preferred data set is fully dominated by any other tuples in the preferred data set.