Abstract
In this paper, we consider the problem of evaluating the continuous query of finding the \(k\) nearest objects with respect to a given point object \(O_{q}\) among a set of \(n\) moving point-objects. The query returns a sequence of answer-pairs, namely pairs of the form \((I,\, S)\) such that \(I\) is a time interval and \(S\) is the set of objects that are closest to \(O_{q}\) during \(I\). When there is uncertainty associated with the locations of the moving objects, \(S\) is the set of all the objects that are possibly the \(k\) nearest neighbors. We analyze the lower bound and the upper bound on the maximum number of answer-pairs, for the certain case and the uncertain case, respectively. Then, we consider two different types of algorithms. The first is off-line algorithms that compute a priori all the answer-pairs. The second type is on-line algorithms that at any time return the current answer-pair. We present algorithms for the certain case and the uncertain case, respectively, and analyze their complexity. We experimentally compare different algorithms using a database of 1 million objects derived from real-world GPS traces.
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Notes
Better complexity is known for kinetic heap when the distance functions are pseudo-lines (i.e., any pair of distance functions intersect each other at most once) (see [6]). In our problem, the square-distance functions are parabolas. Observe that each parabola can be cut into two pseudo-lines. However, this will make the square-distance functions partially defined, whereas the analysis in [6] assumes totally defined functions.
In the computational geometry literature, the level of a point \(p\) is defined to be the number of curves lying strictly below \(p\). In this paper, we define the level to be the number of curves not above \(p\), so that the \(k\)-level corresponds to the \(k\)-th nearest neighbor. But this definition is purely terminological without affecting any results.
See [7] for the definition of Ackermann’s function.
Strictly speaking, the minimum possible distance is zero when \(d_{i}(t)-r_{i}\le 0\), which occurs when the location of \(\hbox {O}_{\mathrm{q}}\) at t falls into the uncertainty region \(\hbox {U}_{\mathrm{i}}\hbox {(t)}\). In this case, the min-curve is a parabola truncated by the horizontal line y=0. However, for simplicity of presentation, we assume that \(d_{i}(t)-r_{i}\) is greater than zero for all values of t. But all the results in this paper hold for the case where \(d_{i}(t)-r_{i}\) may be smaller than or equal to zero.
References
Hornsby, K., Egenhofer, M.: Modeling moving objects over multiple granularities. Ann. Math. Artif. Intell. 36(1–2), 177–194 (2002)
Weiss, M.A.: Data Structures and Algorithms Analysis in C++. Benjamin/Cummings, Reading (1994)
Li, Y., Yang, J., Han, J.: Continuous K-Nearest Neighbor Search for Moving Objects. SSDBM pp. 123–126 (2004)
Iwerks, G., Samet, H., Smith, K.: Continuous K-Nearest Neighbor Queries for Continuously Moving Points with Updates. VLDB (2003)
Basch, J., Guibas, L.J.: Data structures for mobile data. J. algorithm 31, 1–28 (1999)
da Fonseca, G.D., de Figueiredo, C.M.H.: Kinetic heap-ordered trees: tight analysis and improved algorithms. Inf. Process. Lett. 85(3), 165–169 (2003)
Huang, Y., Lee, C.: Efficient evaluation of continuous spatio-temporal queries on moving objects with uncertain velocity. Geoinformatica 14, 163–200 (2010)
Agarwal, P.K., Sharir, M.: Davenport-schinzel sequences and their geometric applications. In: Sack, J.R., Urrutia, J. (eds.) Handbook of computational geometry. North-Holland, Amsterdam (2000)
Agarwal, P.K., Sharir, M.: Arrangements and Their Applications. In: Sack, J.R., Urrutia, J. (eds.) Handbook of Computational Geometry. North-Holland, Amsterdam (2000)
Trajcevski, G., Tamassia, R., Ding, H., Scheuermann, P., Cruz, I.: Continuous probabilistic nearest-neighbor queries for uncertain trajectories. EDBT (2009)
Huang, Y., Hen, C., Lee, C.: Continuous K-nearest neighbor query for moving objects with uncertain velocity. Geoinformatica 13, 1–25 (2009)
Huang, Y., Liao, S., Lee, C.: Evaluating continuous K-nearest neighbor query on moving objects with uncertainty. Inf. Syst. 34, 415–437 (2009)
Cheng, R., Kalashnikov, D.V., Prabhakar, S.: Querying imprecise data in moving object environments. TKDE 16(9), 1112–1127 (2004)
Trajcevski, G., Tamassia, R., Cruz, I.F., Scheuermann, P., Hartglass, D., Zaimerowski, C.: Ranking continuous nearest neighbors for uncertain trajectories. VLDB J. 20(5), 767–791 (2011)
Mokhtar, H., Su, J., Ibarra, O.: On Moving Object Queries. PODS (2002)
Song, Z., Roussopoulos, N.: K-nearest neighbor search for moving query point. SSTD, (2001)
Kolahdouzan, M. Shahabi, C.: Continuous K-nearest neighbor queries in spatial network databases. In: STDBM (2004)
Xiong, X., Mokbel, M., Aref, W.: SEA-CNN: scalable processing of continuous K-nearest neighbor queries in spatio-temporal databases. In: ICDE (2005)
Sistla, A., Wolfson, O., Xu, B., Rishe, N.: Answer-pairs and processing of continuous nearest-neighbor queries. In: Proceedings of the 7th International Workshop on Foundations of Mobile Computing, San Jose, CA (2011)
Clarkson, K.L., Shor, P.W.: Applications of random sampling in computational geometry, II. Discrete Comput. Geom. 4(1), 387–421 (1989)
SJU Traffic Information Grid Team, Grid Computing Center. Shanghai taxi trace data. http://wirelesslab.sjtu.edu.cn/download.html
Mokbel, M., Chow, C., Aref, W.G.: The new casper: query processing for location services without compromising privacy. In: VLDB (2006)
Wolfson, O., Jiang, L., Sistla, P., Chamberlain, S., Rishe, N., Deng, M.: Databases for tracking mobile units in real time. In: ICDT (1999)
Guting, R.H., Schneider, M.: Moving Objects Databases. Morgan Kaufmann, Los Altos (2005)
Prabhakar, S., Xia, Y., Kalashnikov, D., Aref, W.G., Hambrusch, S.: Query indexing and velocity constrained indexing: scalable techniques for continuous queries on moving objects. IEEE Trans. Comput. 15(10), 1124–1140 (2002)
Saltenis, S., Jensen, C.S., Leutenegger, S.T., Lopez, M.A.: Indexing the positions of continuously moving objects. In: ACM SIGMOD (2000)
Chen, J., Cheng, R.: Efficient evaluation of imprecise location-dependent queries. In: ICDE (2007)
Cheng, R., Chen, L., Chen, J., Xie, X.: Evaluating probability threshold k-nearest-neighbor queries over uncertain data. In: EDBT (2009)
Sistla, P.A., Wolfson, O., Chamberlain, S., Dao, S.: Querying the uncertain position of moving objects. In: Temporal Databases: Research and Practice (1998)
Cheng, R., Kalashnikov, D., Prabhakar, S.: Evaluating probabilistic queries over imprecise data. In: ACM SIGMOD (2003)
Chen, J., Cheng, R., Mokbel, M., Chow, C.: Scalable processing of snapshot and continuous nearest-neighbor queries over one-dimensional uncertain data. The Very Large Database J. (VLDBJ) 18, 1219–1240 (2009)
Becker, L., Blunck, H., Hinrichs, K., Vahrenhold, J.: A framework for representing moving objects. In: Proceedings of the 15th International Conference on Database and Expert Systems Applications (2004)
Forlizzi, L., Guting, R.H., Nardelli, E., Schneider, M.: A data model and data structures for moving objects databases. In: Proceedings of the ACM SIGMOD International Conference on Management of Data (2000)
Xie, X., Yiu, M., Cheng, R., Lu, H.: Scalable evaluation of trajectory queries over imprecise location data. IEEE Trans. Knowl. Data Eng. (99). doi:10.1109/TKDE.2013.77
Trajcevski, G., Wolfson, O., Hinrichs, K., Chamberlain, S.: Managing uncertainty in moving objects databases. ACM Trans. database Syst. (TODS) 29(3), 463–507 (2004)
Acknowledgments
This research was supported in part by the US Department of Transportation National University Rail Center (NURAIL); Illinois Department of Transportation (METSI); and National Science Foundation grants IIS-1213013, CCF-1216096, DGE-0549489, IIP-1315169, CCF-0916438, CNS-1035914, CCF-1319754, CNS-1314485.
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Sistla, A.P., Wolfson, O. & Xu, B. Continuous nearest-neighbor queries with location uncertainty. The VLDB Journal 24, 25–50 (2015). https://doi.org/10.1007/s00778-014-0361-2
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DOI: https://doi.org/10.1007/s00778-014-0361-2