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Object-Oriented Modeling of Geodata as a Basic Tool for the Integration of Heterogeneous Paleoecological Information
GAERTNER, Holger (email@example.com), University of Bonn, Department of Geography, Meckenheimer Allee 166, D-53115 Bonn, Germany; BERGMANN, Andreas, University of Bonn, Institute of Computer Science III, Römerstrasse 164, D-53117 Bonn, Germany
Key Words: object-oriented modeling, UML, data integration, distributed databases, geomorphology
The increasing use of new techniques within Geo Sciences for capturing field data, and the ongoing development of geographic information systems (GIS), is coupled with a growing diversity of methods such as geomorphological mapping, analyses of sediment covers, hydrological modeling, or dating methods. Furthermore, capturing and analyzing data followed by knowledge-based interpretations of these analyses means high investment of equipment, manpower, and specific knowledge to gain new information about natural processes. The diversity of techniques and methods leads to a vast and further growing amount of heterogeneous data that are stored in diverse formats and in different databases, often even in a single research group. As a consequence, high investments have been made to create central databases to avoid the loss of data as well as to get the possibility to use these data for further research in the same or different research areas. Further specific query components were coupled to these databases for getting easy data access. The existence of several worldwide databases and query systems leads to a number of problems. First of all, the structure of different central databases is often diverse. Furthermore, this argument also applies to the query components. This means, to connect databases or even data sets, special transfer algorithms have to be developed, and the possibility of losing data in the sense of not getting information about their existence is high. An important precondition in order to facilitate integrated access to heterogeneous information is to adequately model and represent the semantics of the different source data sets. The paper focuses on our experiences gained using an object-oriented modeling technique to describe diverse data used in paleoecologic research. The work is carried out in the context of a joint research project, named OPALIS, by Geographers and Computer Scientists at the University of Bonn. The overall goal is to develop an open GIS architecture supporting uniform exploration of distributed heterogeneous data pools. We present problems in sampling, documenting, and modeling both existing data and methods for data storage; therefore, several German research groups within the IGBP-PAGES program were selected as cooperative partners. The advantage of creating basic semantic models (including all metainformation) and representative object-oriented models for each group using the Unified Modeling Language (UML) will be discussed. The UML has been used as a "common language" between computer scientists and geo scientists in the project. The use of this modeling technique allows us to represent different data pools in basically unique models without changing the data sets themselves in any way, as must be done in common databases.