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Proceedings of the fourteenth annual ACM symposium on Parallel algorithms and architectures
External-Memory Breadth-First Search with Sublinear I/O
ESA '02 Proceedings of the 10th Annual European Symposium on Algorithms
Multi-Way Distance Join Queries in Spatial Databases
Geoinformatica
Efficient trajectory joins using symbolic representations
Proceedings of the 6th international conference on Mobile data management
Closest-Point-of-Approach Join for Moving Object Histories
ICDE '06 Proceedings of the 22nd International Conference on Data Engineering
Power law and exponential decay of inter contact times between mobile devices
Proceedings of the 13th annual ACM international conference on Mobile computing and networking
Modeling vanet deployment in urban settings
Proceedings of the 10th ACM Symposium on Modeling, analysis, and simulation of wireless and mobile systems
Generic mobility simulation framework (GMSF)
Proceedings of the 1st ACM SIGMOBILE workshop on Mobility models
Scalable network distance browsing in spatial databases
Proceedings of the 2008 ACM SIGMOD international conference on Management of data
Algorithms and data structures for external memory
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A Lagrangian approach for storage of spatio-temporal network datasets: a summary of results
Proceedings of the 18th SIGSPATIAL International Conference on Advances in Geographic Information Systems
GRAIL: scalable reachability index for large graphs
Proceedings of the VLDB Endowment
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SSTD'11 Proceedings of the 12th international conference on Advances in spatial and temporal databases
BUBBLE Rap: Social-Based Forwarding in Delay-Tolerant Networks
IEEE Transactions on Mobile Computing
Simple, fast, and scalable reachability oracle
Proceedings of the VLDB Endowment
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With the advent of reliable positioning technologies and prevalence of location-based services, it is now feasible to accurately study the propagation of items such as infectious viruses, sensitive information pieces, and malwares through a population of moving objects, e.g., individuals, mobile devices, and vehicles. In such application scenarios, an item passes between two objects when the objects are sufficiently close (i.e., when they are, so-called, in contact), and hence once an item is initiated, it can penetrate the object population through the evolving network of contacts among objects, termed contact network. In this paper, for the first time we define and study reachability queries in large (i.e., disk-resident) contact datasets which record the movement of a (potentially large) set of objects moving in a spatial environment over an extended time period. A reachability query verifies whether two objects are "reachable" through the evolving contact network represented by such contact datasets. We propose two contact-dataset indexes that enable efficient evaluation of such queries despite the potentially humongous size of the contact datasets. With the first index, termed ReachGrid, at the query time only a small necessary portion of the contact network which is required for reachability evaluation is constructed and traversed. With the second approach, termed ReachGraph, we precompute reachability at different scales and leverage these precalculations at the query time for efficient query processing. We optimize the placement of both indexes on disk to enable efficient index traversal during query processing. We study the pros and cons of our proposed approaches by performing extensive experiments with both real and synthetic data. Based on our experimental results, our proposed approaches outperform existing reachability query processing techniques in contact networks by 76% on average.