DIRECT: a query facility for multiple databases
Ulla Merz, Roger King · ACM Transactions on Information Systems · 1994
The subject of this research project is the architecture and design of a multidatabase query facility. These databases contain structured data, typical for business applications. Problems addressed are: presenting a uniform interface for retrieving data from multiple databases, providing autonomy for the component databases, and defining an architecture for semantic services. DIRECT is a query facility for heterogeneous databases. The databases and their definitions can differ in their data models, names, types, and encoded values. Instead of creating a global schema, descriptions of different databases are allowed to coexist. A multidatabase query language provides a uniform interface for retrieving data from different databases. DIRECT has been exercised with operational databases that are part of an automated business system.