A Data Model for Moving Objects Supporting Aggregation

Moving objects databases (MOD) have been receiving increasing attention from the database community in recent years, mainly due to the wide variety of applications that technology allows nowadays. Trajectories of moving objects like cars or pedestrians, can be reconstructed by means of samples describing the locations of these objects at certain points in lime. Although there are many proposals for modeling and querying moving objects, only a small part of them address the problem of aggregation of moving objects data in a GIS (Geographic Information Systems) scenario. In previous work we presented a formal model where the geometric components of the thematic layers in a GIS are represented as an OLAP (On Line Analytical Processing) dimension hierarchy, and introduced the notion of spatial aggregation. In this paper we extend this proposal in order to address moving object aggregation over a GIS. In this way. complex aggregate queries can be expressed in an elegant fashion. We present the data model, characterize the kinds of queries that may appear in this scenario, and show how these queries can be expressed as an aggregation over the result given by a first order formula expressing constraints over the geometries of the layers.