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Mediators for Interoperability: The USM* System

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T his research is aimed at developing a formal semantic model, a theoretical framework, and methodology to facilitate interoperability among distributed and heterogeneous geographic database systems. The primary objective is to develop techniques to identify and resolve various data and schema level conflicts among multiple information sources. Set theory is used to formalize the semantic model (called USM*), which supports explicit modeling and representation of the complex nature of geographic data objects. A comprehensive framework for classifying semantic conflicts has been developed. The framework is then used as a basis for automating the detection and resolution of conflicts among heterogeneous databases. While the focus is on geographic databases, the work is applicable to non-geographic databases as well. A methodology for conflict detection and resolution has been developed to provide interoperability. The methodology is based on the concept of a “mediator? Several types of mediators and an ontology called SCROL for have been defined to provide mediation services.

A software toolkit called USM* that embeds these concepts has been implemented. This toolkit has several components including:

(a) A modeling system that allows users to develop a semantic model to describe their local databases and the federated or global schema

(b) An ontology definition system that allows users to define different types of semantic conflicts and also map from their local schema or federated to the ontology

(c) A mapping tool to map from the federated schema to the local schemas

(d) A query tool that allows the federated schema to be used in accessing the individual databases for queries.

The entire tool kit has been implemented in Java using a three-tier architecture. Oracle is used as the backend for storing the repository of metadata and ontology. The system can be accessed through any Java enabled web browser. We have evaluated the utility of the system and tested it out using several case studies. The results of our evaluation indicate that mediators based systems hold great promise for integrating disparate data sources on the web.

Sponsor: NSF, NASA and IBM


Please click HERE for a PowerPoint presentation of the project.

Please click HERE for a demonstration of the system.

Please click HERE for a Semantic Modeling Support for Geographic Information Systems.

For more information, please contact us.