indexforcitytrajectories-文庫(kù)吧
2025-09-14 01:48 本頁(yè)面
【正文】 The R*tree (cont.) R1 R2 R5 R3 R4 R6 P1 P2 P3 P4 P5 P6 P8 P7 P1 P2 P3 P4 P5 P6 P7 P8 R5 R6 R1 R2 R3 R4 currentAU ? At a certain time, in each road segments, several currentAU exits, the movement of currentAU is performed as function of time. ? currentAU is created by relatively strict rules according to the features of traffic system, so they scarcely expend too much and will not cause significant overlaps. MAP pastAU ? PastAU is designed for indexing vehicle’s historical movements. ? An interesting property about the history records is that the tuples are sorted by their end time stamps, so we can store these history records in the end time order. ? We save the currentAU as pastAU, to meet the need of history query, we store these history records in the form of data stream. CurrentAU amp。 PastAU ? CurrentAU is a finite sequences of tuples. ? PastAU is a possibly infinite sequences of tuples, so it can be represented to be a stream. ? Streams e with the natural (partial) order implied by their time attribute. Indexing Moving Objects ? Index on moving objects can be classified into two different types: ? one is indexing current and anticipated future positions of moving object ? TPRtree (timeparameterized Rtree) [11] is a balanced, multiway tree with the structure of an Rtree that can answer prediction queries on moving objects. ? the other is indexing histories of the positions of moving objects ? mainly focus on summarized data (or aggregate information) ? Aggregate Rtree What is data stream ? ? A data stream is a continuous, timevarying, unbounded sequence of dataitems. Stream items usually take the form of relational tuples that are disposed after they get processed, implying that online stream algorithms are restricted to only one pass over the data. Data arrival rates are arbitrary and cannot be controlled by the processing system. They are unpredictable and fluctuate vastly over
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