Several spatio-temporal applications require the retrieval of summarized information about moving objects that lie in a query region during a query interval (e.g., the number of mobile users covered by a cell, traffic volume in a district, etc.). Existing solutions have the distinct counting problem: if an object remains in the query region for several timestamps during the query interval, it will be counted multiple times in the result. The paper solves this problem by integrating spatio-temporal indexes with sketches, traditionally used for approximate query processing. The proposed techniques can also be applied to reduce the space requirements of conventional spatiotemporal data and to mine spatio-temporal association rules.
As shown in REF , most of these indexes, like aRB-trees, can suffer from the distinct counting problem, i.e., if an object remains in the query region for several timestamps during the query interval, it will be counted multiple times in the result.
Spatio-temporal aggregation using sketches
Proceedings. 20th International Conference on Data Engineering
Proceedings. 20th International Conference on Data Engineering
Computer Science