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Basic Research Actions for a Geographic Object-Oriented Database System

Objective

The goal of the BASIC GOODS working group was to identify the most relevant features of an environment for the effective representation and management of sets of geographic data. It is inherent to this kind of data that these sets tend to become very large, so that the database management system (DBMS) handling them needs to be very efficient.
This Working Group aimed to fix the precise requirements for such an environment and find solutions to the problems that arise from the specific characteristics of the modelled data.
The impact of object oriented data models and languages on the effective representation and management of spatial data was assessed. Specific aims were to extend and/or modify existing object oriented systems to model and manage geographical information and to find specific solutions for the treatment of spatial data, mainly at the level of how this data is actually stored.

Original data models (both extended relational and graph based) for the representation of spatial data have been proposed and tested at the implementation level. The applicability of the object oriented approach to data modelling to the same problem has been examined. This has led to a better understanding of the power and the potential of different nonrelational approaches to the management of spatial data.

New data structures for the (physical) representation of spatial information have been introduced, with special regard to data structures for secondary memory. An extensive analysis of the efficiency of such spatial data structures has been performed. Such data structures favourably compare with preceding proposals regarding efficiency of access to physical information in different types of spatial queries.

Geometric algorithms have been proposed for relevant problems in spatial data organization and access. Special regard has been given to the study of efficient methods for maintaining information derived from spatial data under dynamic conditions (insertion/deletion of data, moving data) and to the representation of spatial data of different scales and at different levels of detail.
APPROACH AND METHODS
Data management is concerned with two aspects of the data itself: the logical level, which defines how the data is represented and how a user can view and handle the data; and the physical level, which defines how the data is stored on a physical medium, such as a hard disk. For the first aspect, object-oriented data models are considered. These are compared both with each other and with more conventional approaches, such as relational models. The work-plan was to:
-define an object-oriented data-model for the representation and treatment of geographic data that allows modelling of both the characteristics of the represented entities and their constraints
-study advanced access methods at the physical level for geometric and descriptive data.
PROGRESS AND RESULTS
Original data models (both extended relational and graph based) for the representation of spatial data have been proposed and tested at the implementation level. The applicability of the Object Oriented approach to data modeling to the same problem has been examined. This has led to a better understanding of the power and the potential of different non relational approaches to the management of spatial data.
New data structures for the (physical) representation of spatial information have been introduced, with special regard to data structures for secondary memory. An extensive analysis of the efficiency of such spatial data structures has been performed. Such data structures favorably compare with preceding proposals regarding efficiency of access to physical information in different types of spatial queries.
Geometric algorithms have been proposed for relevant problems in spatial data organization and access. Special regard has been given to the study of efficient methods for maintaining information derived from spatial data under dynamic conditions (insertion/deletion of data, moving data) and to the representation of spatial data at different scales and at different levels of detail.
POTENTIAL
The research activities conducted within Basic Goods contribute to show the potential of the object oriented approach for the integrated representation and the effective treatment of spatial data. The activities also show how such an approach can be supported by the use of efficient access methods and algorithms for the management of data at physical level.

Coordinator

Università degli Studi di Roma 'La Sapienza'
Address
Via Eudossiana 18
00184 Roma
Italy

Participants (6)

Albert-Ludwigs-Universität Freiburg
Germany
Address
Werthmannsplatz
79100 Freiburg
Algotech
Italy
Address
Via Appia Nuova 310
00183 Roma
Consiglio Nazionale delle Ricerche (CNR)
Italy
Address
Via O. Raimondo, 7
00173 Roma
Consiglio Nazionale delle Ricerche (CNR)
Italy
Address
Via Cesare De Lollis 12
00185 Roma
Fernuniversität Gesamthochschule Hagen
Germany
Address
Feithstraße 140
58097 Hagen
Institut National de Recherche en Informatique et en Automatique - INRIA
France
Address
Domaine De Voluceau-rocquencourt
78153 Le Chesnay