Modeling and Querying Moving Objects

2003

In this chapter we develop DBMS data models and query languages to deal with geometries changing over time. In contrast to most of the earlier work on this subject, these models and languages are capable of handling continuously changing geometries, or moving objects. We focus on two basic abstractions called moving point and moving region. A moving point can represent an entity for which only the position in space is relevant. A moving region captures moving as well as growing or shrinking regions.

Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems - PODS '02, 2002

Database applications for moving objects pose new challenges in modeling, querying, and maintenance of objects whose locations are rapidly changing over time. Previous work on modeling and querying spatio-temporal databases and constraint databases focus primarily on snapshots of changing databases. In this paper we study query evaluation techniques for moving object databases where moving objects are being updated frequently. We consider a constraint database approach to moving objects and queries. We classify moving object queries into: "past", "continuing", and "future" queries. We argue that while traditional constraint query evaluation techniques are suitable for past queries, new techniques are needed for continuing and future queries. Motivated by nearest-neighbor queries, we define a query language based on a single "generalized distance" function f mapping from objects to continuous functions from time to R. Queries in this language may be past, continuing, or future. We show that if f maps to polynomials, queries can be evaluated efficiently using the plane sweeping technique from computational geometry. Consequently, many known distance based queries can be evaluated efficiently.

2008

Trajectory properties are spatio-temporal properties that describe the changes of spatial (topological) relationships of one moving object with respect to regions and trajectories of other moving objects. Trajectory properties can be viewed as continuous changes of an object’s location resulting in a continuous change in the topological relationship between this object and other entities of interest. In this paper we develop a query language TQ for expressing trajectory properties. Our model and query language are based on the framework of constraint query languages. We present some preliminary complexity and expressive power results for the proposed language. 1

Lecture Notes in Computer Science, 2002

We address a fundamental question concerning spatio-temporal database systems: "What are exactly spatio-temporal queries?" We define spatio-temporal queries to be computable mappings that are also generic, meaning that the result of a query may only depend to a limited extent on the actual internal representation of the spatio-temporal data. Genericity is defined as invariance under transformations that preserve certain characteristics of spatio-temporal data (e.g., collinearity, distance, velocity, acceleration, ...) that are relevant to a database user. These transformations also respect the monotone nature of time. We investigate different genericity classes relative to the constraint database model for spatio-temporal databases and we identify sound and complete languages for the first-order, respectively the computable, queries in these genericity classes.

ACM SIGAPP Applied Computing Review, 2012

This paper deals with the design and implementation of a data model and operations for dealing with continuously changing spatial data in Oracle 11g object-relational DBMS. The data model relies on abstract data types but we introduce modifications to the internal structure of the spatiotemporal data representations proposed in the literature, to reduce storage requirements and to enable the reuse of data during the execution of queries. We show how to implement spatiotemporal operations relying on the spatial functions released by the underlying DBMS and how to use the alternative data representations to reduce the volume of temporary data created in the evaluation of spatiotemporal operations. We also demonstrate how to use the proposed data types and operations for storage and manipulation of moving objects data using SQL. Finally, we discuss on the advantages and disadvantages of the proposed solutions. 1

Proceedings Eighth International Symposium on Temporal Representation and Reasoning. TIME 2001, 2001

The development of any comprehensive proposal for spatio-temporal databases involves significant extensions to many aspects of a non-spatio-temporal architecture. One aspect that has received less attention than most is the development of a query calculus that can be used to provide a semantics for spatio-temporal queries and underpin an effective query optimization and evaluation framework. In this paper, we show how a query calculus for spatiotemporal object databases that builds upon the monoid calculus proposed by Fegaras and Maier for ODMG-compliant database systems can be developed. The paper shows how an extension of the ODMG type system with spatial and temporal types can be accommodated into the monoid approach. It uses several queries over historical (possibly spatial) data to illustrate how, by mapping them into monoid comprehensions, the way is open for the application of a logical optimizer based on the normalization algorithm proposed by Fegaras and Maier.

Geoinformatica, 2011

This paper presents a novel approach to express and evaluate the complex class of queries in moving object databases called spatiotemporal pattern queries (STP queries). That is, one can specify temporal order constraints on the fulfillment of several predicates. This is in contrast to a standard spatiotemporal query that is composed of a single predicate. We propose a language design

ACM Transactions on Database Systems, 2004

This article addresses the problem of managing Moving Objects Databases (MODs) which capture the inherent imprecision of the information about the moving object's location at a given time. We deal systematically with the issues of constructing and representing the trajectories of moving objects and querying the MOD. We propose to model an uncertain trajectory as a three-dimensional (3D) cylindrical body and we introduce a set of novel but natural spatio-temporal operators which capture the uncertainty and are used to express spatio-temporal range queries. We devise and analyze algorithms for processing the operators and demonstrate that the model incorporates the uncertainty in a manner which enables efficient querying, thus striking a balance between the modeling power and computational efficiency.

2003

Abstract Whereas earlier work on spatiotemporal databases generally focused on geometries changing in discrete steps, the emerging area of moving objects databases supports geometries changing continuously. Two important abstractions are moving point and moving region, modelling objects for which only the time-dependent position, or also the shape and extent are relevant, respectively.

Proceedings of the 15th annual ACM international symposium on Advances in geographic information systems - GIS '07, 2007

Many database applications deal with spatio-temporal phenomena, and during the last decade a lot of research targeted locationbased services, moving objects, traffic jam preventions, meteorology, etc. In strong contrast, there exist only very few proposals for an implementation of a spatio-temporal database system let alone a web-based spatio-temporal information system. This paper describes the design and implementation of a webbased spatio-temporal information system. The system uses Secondo as spatio-temporal DBMS for handling moving objects and MapServer as an OGC-compliant rendering engine for static spatial data. We describe the architecture of the system and compare our system with a standalone application. The paper investigates in detail issues that arise in the context of the web. First, we describe an implementation of a lightweight client that takes advantage of the functionality offered by Secondo and MapServer. Second, we describe how moving objects can be represented in GML. We discuss possible GML representations, propose an extension of GML that uses 3D segments (2D location + time) to represent moving objects, and present experiments that compare the solutions.

Proceedings of the ACM Symposium on Applied Computing, 2012

This paper deals with the design and implementation of a data model and operations for dealing with continuously changing spatial data in object-relational DBMS. The data model relies on abstract data types but we introduce modifications to the internal structure of the spatiotemporal data representations proposed in the literature, to reduce storage requirements and to enable the reutilization of data during the execution of the queries. We show how to implement spatiotemporal operations relying on the spatial functions released by the underlying DBMS and how to use the alternative data representations to reduce the volume of temporary data created in the evaluation of spatiotemporal operations. We also discuss on the advantages and disadvantages of the proposed solutions.

Proc. 6th International Conference on Principles and Practice of Constraint Programming, 2000

In this paper we propose a new data model called periodic spatiotemporal objects (PSOs) databases. We show that relational algebra can be extended to PSO databases and any fixed relational algebra queries can be evaluated in PTIME in the size of any input database. We also describe a database system implementation of the PSO model and several sample queries.

International Journal of Database Management Systems, 2012

KEYWORDS Trajectory meta-model, moving object database, space time path, space time ontology, event ontology, trajectory meta-model.

2007 IEEE 23rd International Conference on Data Engineering Workshop, 2007

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 time. 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.

Proceedings of the 5th ACM international workshop on Data engineering for wireless and mobile access - MobiDE '06, 2006

Composition of temporal and spatial properties of real world objects in a unified data framework results into Moving Object Databases (MOD). MODs are able to process, manage and analyze discretely or continuously changing spatio-temporal data. This paper presents HERMES Moving Data Cartridge, which provides MOD functionality to OpenGIS-compatible state-of-theart Object-Relational DBMS. HERMES is designed to be used as a pure temporal or a pure spatial system, however, its main application is to support modeling and querying of moving objects. A relevant collection of abstract data types (ADT) and their corresponding operations are defined, developed and provided as a data cartridge extending SQL-like query languages with MOD semantics. The usefuleness of the resulting query language is demonstrated by developing an application on top of this framework, which builds and visualizes the results of a palette of spatio-temporal queries that have been proposed in the literature as an advanced Location-Based Services (LBS) benchmarking framework for the evaluation of MOD engines.