Multidatabase Querying by Context

The overwhelming acceptance of the SQL standard [10] has curtailed continuing research work in relational database query languages and processing. Since all commercial relational database systems conform with the SQL standard, there is little motivation for developing new query languages. Despite its benefits and wide-spread acceptance, SQL is not a perfect query language. Complex database schema challenge even experienced database users during query formulation. As increasing numbers of less sophisticated users access numerous data sources within an organization or across the Internet, their ability to accurately construct queries with the appropriate structure and semantics diminishes. SQL can be hard to use as it provides only physical access transparency not logical transparency. That is, a user is responsible for mapping the semantics of their query to the semantics and structure of the database. Although graphical tools for query construction and high-level programming languages mask some of the complexity, the notion of querying by structure is intrinsic to most forms of data access. In this work, we overview a new query language developed in conjunction with our integration architecture for automatically integrating relational schema. Although the major focus of this work is on database interoperability, the contribution of this paper is a language for specifying queries on the integrated view produced. The complexities of querying across database systems and resolving conflicts are too numerous to be fully described here, so this paper will discuss querying the integrated view of a