Generating Spatio-Temporal Streaming Trajectories

Recent research efforts in data stream management systems (DSMS) focus mainly on processing continuous queries over traditional data streams, and only a few addressed spatio-temporal continuous queries. OCEANUS presents an effort to extend TelegraphCQ DSMS with spatial support providing a platform for spatio-temporal streaming applications. Data type system that represents the formal basis for modeling moving objects in data streams, as well as an approach for managing moving objects in spatio-temporal data streams based on user-defined aggregate functions (UDAF) are presented. In this paper we are concerned with improving proposed approach for extracting moving objects out of spatio-temporal data streams based on UDAF. It is based on two methods for detecting static locations on trajectories of moving objects and for reducing total number of units in sliced representation by introducing trajectory buffer. First method leads to more precise results of certain operations over moving objects such as retrieving information about speed and direction, but also enables introduction of few new operations such as retrieving static locations and overall stoppage time on moving object's trajectory. Second method leads to better memory usage during processing spatio-temporal continuous queries in DSMS.