Review of Relational Algebra for Query Processing in Dynamic Distributed Federated Databases

This paper reviews the coverage of formal Relational Algebra as it applies to distributed, federated databases in varying network topologies. The review shows that a number of Relational Algebra extensions allow distributed relations and federation of heterogeneous database schema. More concrete physical Relational Algebra extensions support access plans for multi-database query processing but lack cost functions dealing with specific network topologies such as scale-free networks, hyper-cubes and Kautz graphs. Statistic gathering techniques are highlighted which allow efficient distribution of database metrics, with the aim of providing optimized query processing.