Subspace Skyline Queries

Abstract

Skyline queries help users make intelligent decisions over complex data, when different and often conflicting criteria are considered. Such queries return a set of data points that are not dominated by any other point on all dimensions. Skyline queries have been studied in centralized systems and more recently in distributed environments, such as web information systems and peer-to-peer (P2P) networks. Skyline query processing in P2P networks poses inherent challenges and demands non-traditional techniques due to the distribution of content and the lack of global knowledge. Distributed skyline processing should minimize transfer of globally dominated data points. Moreover, peers that do not store any global skyline points, ideally should not be contacted at all. Detecting domination between points that are stored by different peers is challenging and requires usage of summary information that describes the data stored locally and across the network. In this section, we describe in details a distributed framework for subspace skyline processing, called SKYPEER+ [130]. SKYPEER+ reduces both computational time and volume of transmitted data due to (i) efficient routing of skyline queries over the super-peer network, and (ii) an effective thresholding and indexing scheme for discarding dominated points.