Representation and Manipulation of Moving Points: An Extended Data Model for Location Estimation

Abstract

The fields of application of spatio-temporal systems, i.e., systems that must operate with time-varying spatial properties, are vast and heterogeneous. Since it would be difficult to treat such diversity as a whole, we introduce a classification for spatio-temporal systems based on the properties of the represented objects. Building on this classification, we also claim that features of some complex objects can be derived from those of simpler ones, suggesting an evolutionary approach, starting with the study of simple objects and progressing by enriching them with new features. This paper focuses on the definition of a data model for representation of moving points. The model is based on the decomposition of the trajectory of moving points into sections. The movement within each section of a trajectory is described by a variability function. Since, for most systems, it is not possible to store the exact knowledge about the movement of a mobile, the answers to queries may be imprecise. We propose two additional approaches to deal with imprecision, the superset and the subset semantics, based on a maximum value for the variability function, and a smooth technique to integrate them in the model. Finally, we analyse some functional aspects of the implementation of the data model on a Relational Database Management System (RDBMS) and outline some directions for future research.

Geographical information systems

“…Current work can be found for example in Wolfson (1998), de Caluwe (2004, Petry et al (2005). In Moreira, Ribeiro and Saglio (1999), a data model for representing moving points by a decomposition of a trajectory in several sections is specified. By use of regression techniques, movement within each section is described by a variability function.…”

A GIS-based system for electromagnetic risk management in urban areas

“…Sistla et al 1998, Moreira et al 1999, Pfoser and Jensen 1999, Yanagisawa et al 2003. These considerations require that several kind of data must be integrated to have an entire vision of the analysed phenomena that vary in time and space.…”

Modelling potential movement in constrained travel environments using rough space–time prisms

“…To cope with the problem of finite sampling in moving object databases (MODs), several researchers, among them (Sistla et al 1998), (Moreira et al 1999), (Trajcevski et al 2004), and (Pfoser et al 2005) have sought to delineate and query the unknown path between two observed locations given a presupposed maximum travel velocity in an unconstrained isotropic travel environment. In line with the advances in MODs, time geographers have also studied the sampling problem extensively using time geography's key concept, i.e.…”