1. Continuous Motion Pattern Query
Petko Bakalov, Vassilis J. Tsotras
University of California, Riverside
4/26/2019

2. Motivation
The need to locate spatio-temporal objects that follow specific patterns in streaming environment.
Example:
Tracking the movement of law offenders and alerts the correctional officers for any suspicious or illegal behavior.
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3. Definition
A Continuous Motion Pattern query Q is expressed as a sequence of n spatiotemporal predicates:
Qi is a spatial predicate, Ti is a relative time constraint, Ψi is a logical quantifier
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4. Indexing
We need an appropriate spatiotemporal indexing structure that can accommodate positive and negative updates.
Such structure should answer efficiently questions of the type
Given area A, provide all objects that are not in A at the previous time instant but appear in A at the current instant (a + update)
Provide all objects that do not appear in A in the current time instant but were in A at the previous one (a - update)
Key ideas of the algorithm
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5. One dimensional example
Time To
……..… T2
Data
Pages
Grid
Cells 1 2 3
Time T1 T2
………… T1
Time
From T1 T2 1
Here are the four steps of the algorithm. 2 3
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6. One dimensional example
For any time period ( for example (3;6)) this space can be divided on 4 regions
Time to 3 2
Region 1 7 6
Region 2 5 1 4 4
In this slide we discuss the trajectory approximation.
Region 3 3 2
Region 4 1 1 2 3 4 5 6 7
Time from
4/26/2019