Query Translation Supporting the Migration of Legacy Databases into Cooperative Information Systems

In this paper, we present a query translation algorithm which allows object-oriented queries to be automatically translated into a relational query language. Our goal is to provide a unique and powerful query interface supporting the cooperation of information systems, particularly under the aspect of migrating existing systems without changes into the cooperation. Translation algorithms, like the one proposed in this paper are essential parts of CISs to mediate between the common global query language and the query languages of participating components. Our query translation algorithm ensures a fully automatic translation of object-oriented queries into equivalent SQL queries for the original relational schema in all cases where a direct translation is possible. In all other cases, it generates SQL queries providing a superset of the desired data and a sequence of ‘formatting’ functions that transform the data into the desired result.