A foundation for representing and querying moving objects

Abstract

Spatio-temporal databases deal with geometries changing over time. The goal of our work is to provide a DBMS data model and query language capable of handling such time-dependent geometries, including those changing continuously that describe moving objects . Two fundamental abstractions are moving point and moving region , describing objects for which only the time-dependent position, or position and extent, respectively, are of interest. We propose to present such time-dependent geometries as attribute data types with suitable operations, that is, to provide an abstract data type extension to a DBMS data model and query language. This paper presents a design of such a system of abstract data types. It turns out that besides the main types of interest, moving point and moving region, a relatively large number of auxiliary data types are needed. For example, one needs a line type to represent the projection of a moving point into the plane, or a “moving real” to represent the time-dependent distance of two points. It then becomes crucial to achieve (i) orthogonality in the design of the system, i.e., type constructors can be applied unifomly; (ii) genericity and consistency of operations, i.e., operations range over as many types as possible and behave consistently; and (iii) closure and consistency between structure and operations of nontemporal and related temporal types. Satisfying these goal leads to a simple and expressive system of abstract data types that may be integrated into a query language to yield a powerful language for querying spatio-temporal data, including moving objects. The paper formally defines the types and operations, offers detailed insight into the considerations that went into the design, and exemplifies the use of the abstract data types using SQL. The paper offers a precise and conceptually clean foundation for implementing a spatio-temporal DBMS extension.

An Object-Relational Approach to the Representation of Multi-granular Spatio-Temporal Data

“…A first relevant approach has been developed by Guting et al [16]. The approach supports the change of the position or extension for geometry through the use of abstract data type definition capabilities.…”

“…It develops a set of constructors and query operators in an abstract model thus giving a compact and uniform vision for every data type. In the proposed approach [16], some data types, namely Integer, Boolean, Spatial, can be transformed in a temporal data type. Such an abstract model has been then transformed in a discrete model [14], closer to the implementation but more restricted with respect to the abstract model.…”

“…Therefore, we must specify the observation unit for both space and time. These objects are called moving objects [16]. The Fig.…”

Hermes – A Framework for Location-Based Data Management

“…3G cell-phone or PDA enhanced by the presence of a GPS receiver), receiving hints of information, commercial spots etc. Researchers [1], [2], [3], [4], motivated from such kind of application scenarios have tried to model spatio-temporal databases using this concept of moving objects and integrate them into any extensible DBMS. On the other hand, commercial relational or object-relational database systems offer limited capability of handling this kind of non-traditional data (object trajectories, in time and space).…”

The Geometry of Uncertainty in Moving Objects Databases

“…Modeling and querying location uncertainties due to sampling and GPS imprecision is presented in [16]. Algebraic specifications of a system of abstract data types, their constructors and a set of operations are given in [4,6,9].…”