[Vldb 2013] skyline operator on anti correlated distributions
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Shang, Haichuan, and Masaru Kitsuregawa. "Skyline operator on anti-correlated distributions." Proceedings of the VLDB Endowment 6.9 (2013): 649-660.
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[Vldb 2013] skyline operator on anti correlated distributions
- 1. Skyline Operator on Anti-correlated Distribution Proceedings of the VLDB(2013) Endowment, Vol. 6 No. 9 Haichuan Shang, Masaru Kitsuregawa Presenter: WooSung Choi (ws_choi@korea.ac.kr) DataKnow. Lab Korea UNIV.
- 3. Preliminaries • Formal definition of Dominates (≺) Given a set of d-dimensional points 𝑇 We say that a point t1 ∈ 𝑇 DOMINATES another point t2 ∈ 𝑇 If and only if ∀𝑖 ∈ 1, 2, 3, … , 𝑑 , 𝑡1 𝑖 ≤ 𝑡2[𝑖] ∃𝑗 ∈ 1, 2, 3, … , 𝑑 , 𝑡1 𝑗 < 𝑡2[𝑗] and Denoted by t1 ≺ t2 (simply saying, t1 이 자명하게 선호됨) Definition from http://www.comp.nus.edu.sg/~atung/publication/k_dominant.pdf Note that the meaning of ‘dominates’ may differ according to type of application www.caranddriver.com
- 4. formal Definition (skyline) • The Skyline operator Input - Given a set of objects P = {𝑝1, 𝑝2, … , 𝑝 𝑁} 𝑆𝐾𝑌𝐿𝐼𝑁𝐸 𝑃 = {𝑝𝑖| 𝑝𝑖 ∈ 𝑃 𝑎𝑛𝑑 ∄ 𝑝∗ ∈ 𝑃 𝑠. 𝑡. 𝑝∗ ≺ 𝑝𝑖} A B C D E F Dominating Area(B) x axis yaxis G Common misconceptions “𝐵 ∈ 𝑂𝑢𝑝𝑢𝑡 s𝑖𝑛𝑐𝑒 𝐵 ≺ 𝐶 , D, F” , wrong “𝐵 ∈ 𝑂𝑢𝑝𝑢𝑡, s𝑖𝑛𝑐𝑒 𝑛𝑜 𝑜𝑡ℎ𝑒𝑟 𝑝𝑜𝑖𝑛𝑡 𝑃 ≺ 𝐵”, correct
- 5. Suppose there are n objects in the given set 𝐷 𝑥 = {𝑜1, 𝑜2, … , 𝑜 𝑛} Algorithm -Naïve 1 𝑓𝑜𝑟 𝑒𝑎𝑐ℎ 𝑜𝑏𝑗𝑒𝑐𝑡 𝑜 𝑥 ∈ 𝐷 𝑏𝑜𝑜𝑙𝑒𝑎𝑛 𝑖𝑠𝐷𝑜𝑚𝑖𝑛𝑎𝑡𝑒𝑑 = 𝑓𝑎𝑙𝑠𝑒 𝑓𝑜𝑟 𝑒𝑎𝑐ℎ 𝑜𝑏𝑗𝑒𝑐𝑡 𝑜 𝑦 ∈ 𝐷 𝑖𝑓 ¬(𝑜 𝑥 = 𝑜 𝑦) 𝐴𝑁𝐷 ¬ 𝑜 𝑦 ≺ 𝑜 𝑥 𝑡ℎ𝑒𝑛 𝑐𝑜𝑛𝑡𝑖𝑛𝑢𝑒; 𝑒𝑙𝑠𝑒 𝑡ℎ𝑒𝑛 𝑖𝑠𝐷𝑜𝑚𝑖𝑛𝑎𝑡𝑒𝑑 = 𝑡𝑟𝑢𝑒; break; 𝑖𝑓 ! 𝑖𝑠𝐷𝑜𝑚𝑖𝑛𝑎𝑡𝑒𝑑 𝑆 ∪ {𝑜 𝑥} Naïveapproach NestedLoopStructure Computational Cost - 𝑂(𝑛2 )
- 8. Related Work: Summary • Worst-case Analysis (2.1) worst case complexity on arbitrary data distributions Ω(𝑛𝑙𝑜𝑔𝑛)[16], O( N/B logM/B 𝑑−2 N/B )[12] • Elimination Category (2.2) Average Complexity with dimensional independence Idea: Eliminate non-skyline objects quickly! BNL[7], SFS[9], LESS[12], … O(dnm)[20], where 𝑚 is the skyline cardinalityO(dnm)[20], where 𝑚 is the skyline cardinality
- 10. Anti-Correlated (2) •A relationship in which the value in one dimension increases as the values in the other dimensions decrease •Skyline Queries are used to find a set of non-dominated data points for Multi-Criteria Decision Making •Data in real world is more likely to be anti- correlated
- 11. Anti-Correlated (3) • The anti-correlation significantly limits the practical usage of the existing algorithms • and yields the demand of effective mathematical models and efficient algorithms on anti-correlated data O(dnm)[20], where 𝑚 is the skyline cardinality 𝑚 tends to increase on anti-correlated distribution These existing algorithms fall back to O(dn2)
- 12. 뭘 하겠다는 연구인가? 공헌도
- 13. Contribution • 1) General model for the anti-correlated distribution • 2) Polynomial Estimation of the lower bound of the expected value of skyline cardinality • 3) a “Determination and Elimination Framework” for efficient computation of skyline on anti-correlated distribution
- 14. 3. PRELIMINIARIES Definition & Expectation of Skyline Cardinality
- 15. Model: Anti-Correlated Distribution 0 1000 2000 3000 4000 5000 6000 7000 8000 0 2000 4000 6000 8000 10000 12000 Uniform 0 1000 2000 3000 4000 5000 6000 0 2000 4000 6000 8000 10000 12000 Anti c=1 0 1000 2000 3000 4000 5000 6000 0 2000 4000 6000 8000 10000 12000 Anti c=0.1 1) General model for the anti-correlated distribution
- 16. 1K Tuples 0 1000 2000 3000 4000 5000 6000 7000 8000 0 2000 4000 6000 8000 10000 12000 Uniform 0 1000 2000 3000 4000 5000 6000 0 2000 4000 6000 8000 10000 12000 Anti c=1 0 1000 2000 3000 4000 5000 6000 0 2000 4000 6000 8000 10000 12000 Anti c=0.1 12 57 116 1) General model for the anti-correlated distribution
- 17. 1K Tuples 0 1000 2000 3000 4000 5000 6000 0 2000 4000 6000 8000 10000 12000 Anti c=1 57 𝑆2,1000,1 ≈ 1000 ∗ 𝜋 − 1 = 55.0499122 2) Polynomal Estimation of the lowerbound of the expected value of skyline cardinality
- 18. Generalization • Theorem 3 The expected value 𝑆 𝑑,𝑛,𝑐 of the skyline cardinality 𝑆 𝑑,𝑛,1 ≤ 𝑆 𝑑,𝑛,𝑐 ≤ 𝑆 𝑑,𝑛,0 = 𝑛 𝑆 𝑑,𝑛,1 = 𝑘=1 𝑑 −1 𝑘−1 𝑑−1 𝑘−1 𝑛 Γ 𝑘 𝑑 Γ(n) Γ(𝑛+ 𝑘 𝑑 ) ≈ 𝑘=1 𝑑 −1 𝑘−1 𝑑−1 𝑘−1 Γ 𝑘 𝑑 𝑛1− 𝑘 𝑑 when d ≥ 2 • Where Γ 𝑛 = 1 2𝜋 0 ∞ 𝑒−𝑡 𝑡 𝑛 𝑑𝑡 2) Polynomal Estimation of the lowerbound of the expected value of skyline cardinality O(dnm)[20], where 𝑚 is the skyline cardinality 𝑚 tends to increase on anti-correlated distribution These existing algorithms: O(𝑑𝑛(2𝑑−1)/𝑑) ~ O(dn2)
- 19. Pearson Correlation Coefficient or covariance based model
- 20. 공분산 • 확률론과 통계학에서, 공분산(共分散, 영어: covariance) 은 2개의 확률변수의 상관정도를 나타내는 값 • 만약 2개의 변수중 하나의 값이 상승하는 경향을 보일 때, 다른 값도 상승하는 경향의 상관관계에 있다면, 공분 산의 값은 양수 • 반대로 2개의 변수중 하나의 값이 상승하는 경향을 보일 때, 다른 값이 하강하는 경향을 보인다면 공분산의 값은 음수