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

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. 4/26/2019

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 4/26/2019

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 4/26/2019

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 4/26/2019

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