Query Processing in a Fragmented Relational Distributed System: Mermaid

This paper describes the query optimizer of the Mermaid system which provides a user with a unified view of multiple preexisting databases which may be stored under different DBMS´s. The algorithm is designed for databases which may contain replicated or fragmented relations and for users who are primarily making interactive, ad hoc queries. Although the implementation of the algorithm is a front-end system, not an integrated distributed DBMS, it should be applicable to a distributed DBMS also.