Data Integration for DW Construction

Useful data being distributed over several systems, we have a problem in accessing and utilizing them. Recognizing this problem, researchers have proposed two concepts as solutions to the problem, multidatabase and data warehouse. The one provides a virtual view over the distributed data, and the latter is a materialized view of it. Recently, more attention has been paid to the latter, which is a single of distributed database, collected along a time dimension. So, the major issues in building a data warehouse are 1) how to define a global schema for the data warehouse, 2) how to capture changes from local databases, and 3) how to represent time-varying values of data item. This paper presents an integrated approach to these issues, borrowing the research results from such areas as multidatabase, active databases and temporal databases.