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Processing Monitoring Queries on Mobile Objects

This lecture from the Department of Computer Science at Iowa State University explores the concept of mobile databases, highlighting centralized and decentralized architectures. It delves into the intricacies of range-monitoring queries, which involve retrieving and continuously monitoring mobile objects within a specified spatial region. Key applications include tourism, traffic control, and wildlife tracking. The presentation addresses important research issues, such as minimizing location updates and server processing costs, while introducing concepts like the Domain Tree for efficient query management.

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Processing Monitoring Queries on Mobile Objects

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  1. Processing Monitoring Queries on Mobile Objects CS461 Lecture Department of Computer Science Iowa State University

  2. What is a mobile database? • A mobile database is a set of mobile devices • Centralized: there exists a central server with which each mobile device can communicate • Decentralized: these devices form a network by themselves • Mobile ad hoc network (MANET) • Mesh networks

  3. Characteristics • Large number of mobile objects • Continuous movement of mobile objects • Limited battery power • Limited communication bandwidth

  4. Processing Range-Monitoring Query • What is range-monitoring query? • Retrieve mobile objects in a spatial region, and • continuously monitor the population in the area

  5. Range-Monitoring Queries Q2 a d e Q1 c b f

  6. Range-Monitoring Queries Q2 a d Q1 e b c f

  7. Some Potential Applications • Tourist guiding • Automatic traffic control • Digital battlefield vehicle tracking • Wild animal tracking

  8. Research Issues • How to minimize location updates? • Excessive mobile communication could drain battery power quickly • How to minimize server processing cost? • Query results keep changing

  9. Related Works • Location Estimation [Woflson98, Woflson99, etc.] • Trajectory Indexing [Kollios99, Saltenis00, etc.] • Safe Region Approach [Prabhakar00, Prabhakar01]

  10. Safe Regions Rectangular Safe Region Q1 Q2 Q5 a Q3 Q4 Circular Safe Region

  11. Problems with Safe Regions • Computing a safe region takes from O(n) to O(n log3 n) • Adding a new query requires to re-compute safe regions for all objects

  12. Challenge How to provide • accurate query results, and • real-time updates?

  13. Proposed: Monitoring-Query Management Q1 Q6 Q3 Q2 a Q5 Q7 Q4 Resident Domain

  14. Computing a Resident Domain • Given an object’s position P and its processing capability N, its resident domain should • contain position P, and • be as large as possible, but • contain no more than N queries

  15. Domain and Query Decomposition Q2 Q3 R1 R21 R22 Q1 R31 Q4 R41 R42

  16. Domain and Query Decomposition Q2 Q3 R1 R21 R22 Q1 R31 a Q4 R41 R42

  17. Domain and Query Decomposition Q2 Q3 R1 R21 R22 Q1 R31 a Q4 R41 R42

  18. Domain Tree (D-tree) D domain node D data node

  19. Domain Tree (D-tree) D d1 d2 d1 d2

  20. Domain Tree (D-tree) D d21 d1 d2 d1 d21 d22 d22

  21. Mobile Communication Cost 30 25 20 Safe Region 15 Number of messages sent by mobile objects (millions) MQM 10 5 0 10 20 30 40 50 60 70 80 90 100 Number of monitoring queries (thousands)

  22. Server Processing Cost 1000 100 Safe Region 10 MQM Number of index nodes accessed (millions) 1 0.1 10 20 30 40 50 60 70 80 90 100 Number of monitoring queries (thousands)

  23. Significant and Impact of MQM • MQM is the first scalable technique, in terms of mobile communication and server processing costs, for real-time range-monitoring query management

  24. Questions • Any other types of queries? • Can any type of queries be converted into one or a number of range monitoring query?

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