This paper extends relational processing and optimization to the FISQL/FIRA languages for dynamic schema queries over multidatabases. Dynamic schema queries involve the creation and restructuring of metadata at run time. We present a full implementation of a FISQL/FIRA engine based on our work, which includes subqueries and all transformational capabilities of FISQL/FIRA on distributed, multidatabase platforms. An important application of the system is to enhance traditional information architectures by enabling the creation and maintenance of dynamic wrappers and mapping queries at source databases within GAV, LAV, GLAV, peer-to-peer, or other integration frameworks. In addition to fully supporting FISQL/FIRA on multidatabases, our implementation introduces a bi-level optimization paradigm where purely relational sub-fragments of queries are pushed into source engines. This paradigm shares features of canonical distributed database processing, but has a new dimension through the exte...
Catharine M. Wyss, Felix I. Wyss