Efficient skyline querying with variable user preferences on nominal attributes

Current skyline evaluation techniques assume a fixed ordering on the attributes. However, dynamic preferences on nominal attributes are more realistic in known applications. In order to generate online response for any such preference issued by a user, one obvious solution is to enumerate all possible preferences and materialize all results of these preferences. However, the pre-processing and storage requirements of a full materialization are typically prohibitive. Instead, we propose a semi-materialization method called the IPO-tree Search which stores partial useful results only. With these partial results, the result of each possible preference can be returned efficiently. We have also conducted experiments to show the efficiency of our proposed algorithm.