The skyline operator is important for multicriteria decision-making applications. Although many recent studies developed efficient methods to compute skyline objects in a given space, none of them considers skylines in multiple subspaces simultaneously. More importantly, the fundamental The research of J. Pei was partially supported by NSERC Discovery Grants, NSERC Collaborative Research and Development Grants, NSF Grant IIS-0308001, and IBM Eclipse Innovation Awards. The research of Y. Yuan and Q. Lin was partially supported by ARC Discovery Grant (DP0666428). The research of M. Ester was partially supported by NSERC. The research of Y. Tao was partially supported by the RGC grant CityU 1163/04E from the HKSAR government. The research of J. X. Yu was partially supported by RGC grant (CUHK418205) of HKSAR. All opinions, findings, conclusions and recommendations in this paper are those of the authors and do not necessarily reflect the views of the funding agencies. Authors' addresses: J. Pei, W. Jin, M. Ester, Simon Fraser University, Canada; email: {jpei,wjin,ester}@cs.sfu.ca; Y. Yuan (also NICTA, Australia), X. Lin (also NICTA, Australia), W. Wang, The University of New South Wales, Australia; email: {yyidong,lxue,weiw}@cse.unsw.edu.au; Q. Liu, The University of Queensland, Australia; email: qing@itee.uq.edu.au; Y. Tao, J. X. Yu, The Chinees University of Hong Kong; email: taofy@cs.cityu.edu.hk, yu@se.cuhk.edu.hk; Q. Zhang, E-Health Research Centre/CSIRO ICT Centre, Australia; email: qing.zhang@csiro.au. Permission to make digital or hard copies of part or all of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or direct commercial advantage and that copies show this notice on the first page or initial screen of a display along with the full citation. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, to republish, to post on servers, to redistribute to lists, or to use any component of this work in other works requires prior specific permission and/or a fee. Permissions may be requested from Publications Dept., ACM, Inc., 2 Penn Plaza, Suite 701, New York, NY 10121-0701 USA, fax +1 (212) 869-0481, or permissions@acm.org. In this article, we tackle the problem of multidimensional subspace skyline computation and analysis. We explore skylines in subspaces. First, we propose the concept of SKYCUBE, which consists of skylines of all possible nonempty subspaces of a given full space. Once a SKYCUBE is materialized, any subspace skyline queries can be answered online. However, SKYCUBE cannot fully address the semantic concerns and may contain redundant information. To tackle the problem, we introduce a novel notion of skyline group which essentially is a group of objects that coincide in the skylines of some subspaces. We identify the decisive subspaces that qualify skyline groups in the subspace skylines. The new notions concisely capture the semantics and...
