A Hybrid Aggregate Index Method for Trajectory Data

Algorithm 1

Aggregate query algorithm.

	Algorithm Aggregate_Query (qR, qT, α)
	Input: qR: query area, qT: query time, α: probability threshold
	Output: allnumber: the approximate number of moving objects under this query condition
(1)	Obtain all buckets bi intersected from qR in the UPBI-Sketch and AMH^+-Sketch index according to qR and qT
(2)	The appropriate sketch number M about qR is calculated according to the sketch number mk of each intersected bi (Rk, mk, skk, lifespan[ls, le))
(3)	For RID in qR
(4)	Query all moving objects OID at qT time to generate sketch
	//The probabilistic range query algorithm [42] is combined with the FM_PCSA algorithm [9]
(5)	Use OR operation [9] and replace ADD operation to get all_Sketch
(6)	End for
(7)	Convert all_Sketch to the approximate value allnumber of moving objects by fitting curve [19]
	End Aggregate_Query