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# Query Answering on Trajectory Cuboids using Prime Numbers Encodings

Query Answering on Trajectory Cuboids using Prime Numbers Encodings. Elio Masciari ICAR-CNR. IDEAS Conference Lisbon September2011. Trajectory Data Prime Numbers Encoding for Paths Warehousing Steps Experimental Evaluation Conclusions. Outline.

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## Query Answering on Trajectory Cuboids using Prime Numbers Encodings

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1. Query Answering on Trajectory Cuboids using PrimeNumbersEncodings Elio Masciari ICAR-CNR IDEAS Conference Lisbon September2011

2. Trajectory Data • Prime NumbersEncodingforPaths • WarehousingSteps • ExperimentalEvaluation • Conclusions Outline

3. Data Pertainingtotime and position ofmovingobjects • GPS systems • Traffic management • Twodimensional • In generalpartitioningis a wellacceptedsolution • Segmentation • Regioning Trajectory Data

4. Trajectory Data

5. Regioning • IPCA: IdentifiesPreferredDirectionsfor Data • DifferentialRegioning • Prime NumberEncoding: • Trajectoriesrepresentedasproductsof prime numbers OurSolution: Regioning+Encoding

6. Regioning: regionsclosetoprincipaldirections are finer

7. T1 = ABC crossingthree regions A,B,C. Assign to regions A, B and C respectively the prime numbers 3,5,7 • For trajectory T1 the witness W1 is 52 since 52%3 = 1 = pos(A) and 52%5 = 2 = pos(B) and 52%7 = 3 = pos(C) • Store the encodedtrajectoriesusing a binarytree Encoding: prime numbers

8. Building Specializedcuboids:TRAC • DistinctCountProblem • Measures • the number of distinct trajectories (Intersections), • the average traveled distance (Distance), • the averagetimeintervalduration (Duration) TrajectoryWarehousing

9. Precomputedcuboidspertainingtomostinterestingrecent data • Mergingcuboids at differentgranularitylevelswhenneeded • Iceberg assumption TRACs

10. Performances

11. Performances

12. Performances

13. Performances

14. Data reductionbyregioning • EfficientQueying via Encoding • Warehousing in ordertoallowtrajectoryqueryingeffectively • Goodperformances • Accuracy • Efficiency Conclusions

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