Group spatiotemporal pattern queries

Group spatiotemporal patterns are certain formations, in space and time, shown by groups of moving objects, such as flocks, concurrence, encounter, etc. A large number of recent applications focus on the collective behavior of moving objects, rather than the individual movements. Therefore finding such groups in moving object databases is crucial. There exist, in the literature, smart algorithms for matching some of these patterns. These solutions, however, address specific patterns and require specialized data representation and indexes. They share too little to be integrated into a single system. There is a need for a generic query method that allows users to fill in pattern descriptions, and retrieve the set of matches. In this paper, we propose generic query operators that can consistently express and match a wide range of group spatiotemporal patterns. We formally define these operators, illustrate the evaluation algorithms, and discuss the issues of their integration with moving object database (MOD) systems. These operators have been implemented in the context of Secondo MOD system, and the implementation is available online as open source. Several examples are given to showcase the expressive power of the operators. We have made available scripts that can be invoked from the Secondo interface to automatically repeat some of the experiments in this paper.