Querying Heterogeneous Databases Using Standardized Schemas and SQL

Making databases available for querying both within and across organizations is a vision held by many. Realizing this vision, however, is usually hampered by the existence of heterogeneous database systems, heterogeneous query languages and heterogeneous data semantics. What is needed is a uniform method for accessing these databases. This paper presents a standards based approach in which SQL queries are posed on a standardized schema using an ANSI/NISO-standardized communication protocol (ANSI Z39.50). In particular, this paper focuses on the mapping and optimization considerations when translating queries posed on a standardized schema into queries which can be directly executed on locally implemented databases.