A query based approach for integrating heterogeneous data sources

Abstract

Data available on-line today is spread over heterogeneous data sources like traditional databases or sources of various forms containing unstructured and semistructured data. Obviously, the "technical" availability alone is not at all sufficient for making meaningful use of the existing information, and thus the problem of effectively and efficiently accessing and querying heterogeneous data is an important research issue. One main approach is to integrate the data sources and offer users an a priori defined global schema. Alternatively, there are approaches which implement tools for giving users the possibility to define the global schema themselves. We propose a new approach where heterogeneous sources can be queried through a unified interface and underlying sources are integrated by means of a query language only In this paper, we present extensions to OQL which allow to query structurally heterogeneous data, i.e. structured, semistructured and unstructured data alike, and to integrate data on-the-fly. We also deal with issues of the extensive meta information about sources that is needed for integration.