Facilitating interoperability among heterogeneous geographic database systems: A theoretical framework, a prototype system, and evaluation

摘要

The objective of this research is to develop a formal semantic model, theoretical framework and methodology to facilitate interoperability among distributed and heterogeneous geographic database systems (GDSs). The primary research question is how to identify and resolve various data- and schematic-level conflicts among such information sources. Set theory is used to formalize the semantic model, which supports explicit modeling of the complex nature of geographic data objects. The semantic model is used as a canonical model for conceptual schema design and integration. The intension (including structure, integrity rules and meta-properties) of the database schema is captured in the semantic model. A comprehensive framework classifying various semantic conflicts is proposed. This framework is then used as a basis for automating the detection and resolution of semantic conflicts among heterogeneous databases. A methodology for conflict detection and resolution is proposed to develop interoperable system environment. The methodology is based on the concept of a "mediator." Several types of semantic mediators are defined and developed to achieve interoperability. An ontology is developed to capture various semantic conflicts. The metadata and ontology are stored in a common repository and manipulated by description logic-based operators. A query processing technique is developed to provide uniform and integrated access to the multiple heterogeneous databases. Logic is employed to formalize our methodology, which provides a unified view of the underlying representational and reasoning formalism for the semantic mediation process. A usable prototype system is implemented to provide proof of the concept underlying this work. The system has been integrated with the Internet and can be accessed through any Java-enabled web browser. Finally, the usefulness of our methodology and the system is evaluated using three different cases that represent different application domains. Various heterogeneous geospatial datasets and non-geographic datasets are used during the evaluation phase. The results of the evaluation suggest that correct identification and construction of both schema and ontology-schema mapping knowledge play very important roles in achieving interoperability at the both data and schema levels. The research adopts a multi-methodological approach that incorporates set theory, logic, prototyping, and case study.