Data Management+ Laboratory

Dynamic Skylines Considering Range Queries

Speaker: AdamAdviser: Yuling Hsueh

16th International Conference, DASFAA 2011

Wen-Chi Wang En Tzu Wang Arbee L.P. Chen3

INTRODUCTION

What is “Skyline” ?

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INTRODUCTION

Dynamic skyline considering query- Dynamic skyline query regarding query q retrieves the data points

not dynamically dominated by any other data points, with respect to q.

Dynamically dominated- A data point t (t[1], t[2],…,t[n]) is defined to dynamically dominate

another data point s (s[1], s[2],…,s[n]), with respect to query q (q[1], q[2],…,q[n]), iff

1) |t[i] − q[i]| ≤ |s[i] − q[i]|, i = 1 to n, and ∀2) at least in one dimension, say j, |t[j] − q[j]| < |s[j] − q[j]|.

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INTRODUCTION

1) |t[i] − q[i]| ≤ |s[i] − q[i]|, i = 1 to n, and ∀2) at least in one dimension, say j, |t[j] − q[j]| < |s[j] − q[j]|.

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INTRODUCTION

We turn to find the skyline in a transferred dataset in which all of the data points in the original space are transferred to the other space whose origin is equal to query.

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INTRODUCTION

Query=(2000, 4), C1=(1992, 8), C2=(1995, 8), C3=(1998, 3) = (|1992 − 2000|, |8 − 4|) = (8, 4), = (5, 4) and = (2, 1)

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INTRODUCTION

Dynamic skyline considering range queries

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PRELIMINARIES

Problem Formulation- Given an n-dimensional dataset D and a range query q ([q1, q1'],

[q2, q2'], …, [qn, qn']), where [qi, qi'] is an interval representing the user interests in the ith dimension, i = 1 to n∀ , the dynamic skyline query regarding q returns the data points from D, not dynamically dominated by any other data points, with respect to q.

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PRELIMINARIES

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PRELIMINARIES

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query q ([15, 20], [20, 25]), p8 = (17, 30)(|17 − 17|, |30 − 25|) = (0, 5) P7(|25 − 20|, |25 - 25|) = (5, 0), p3(|25 − 20|, |5 − 20|) = (5, 15)

PRELIMINARIES

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Data Structures Used in Algorithm- Grid index- Multidirectional Z-order curves

Grid index- Each dimension of the n-dimensional space is partitioned into b

blocks, each associated with an equal domain range of r.

PRELIMINARIES

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PRELIMINARIES

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Query cells: (3, 4), (3, 5), (4, 4), and (4, 5), range form: ([3, 4], [4, 5]) Pivot cells:([0, 2], [4, 5]), ([5, 7], [4, 5]), ([3, 4], [0, 3]), and ([3, 4], [6, 7])

PRELIMINARIES

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Z-order curve- point (5, 4) = (101, 100)- the Z-address of (5, 4) is (110010)

Monotonic Ordering of Z-order curve- a data point in a cell with a former order cannot be dominated by

the data points in the cells with the latter order

PRELIMINARIES

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Query (3, 4), p4 = (4, 4) (1, 0), p1 = (1, 6 ) (2, 2)

PRELIMINARIES

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Dynamic Skyline Processing

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Principle of Pruning Strategies

Dynamic Skyline Processing

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Principle of Pruning Strategies

Dynamic Skyline Processing

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Principle of Pruning Strategies

ALGORITHM

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EXPERIMENT

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EXPERIMENT

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EXPERIMENT

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CONCLUSIONS

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Author propose a new problem on dynamic skyline computation regarding a range query.

To efficiently answer this query, Author propose an approach based on the gird index and a newly designed variant of the well-known Z-order curve. By these two components, three efficient pruning strategies are devised, thus avoiding the need to scan the whole dataset for generating the transferred dataset and also reducing the times of dominance checking.

THE END

Thank you for listening!

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THE END

Q & A

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