Abstract

SchemaSQL is a recently proposed extension to SQL for enabling multi-database interoperability. Several recently identified applications for SchemaSQL, however, mainly rely on its ability to treat data and schema labels in a uniform manner, and call for an efficient implementation of it on a single RDBMS. We first develop a logical algebra for SchemaSQL by combining classical relational algebra with four restructuring operators -- unfold, fold, split, and unite -- originally introduced in the context of the tabular data model by Gyssens et al. [GLS96], and suitably adapted to fit the needs of SchemaSQL. We give an algorithm for translating SchemaSQL queries/views involving restructuring, into the logical algebra above. We also provide physical algebraic operators which are useful for query optimization. Using the various operators as a vehicle, we give several alternate implementation strategies for SchemaSQL queries/views. All the proposed strategies can be implemented non-intrusi...

Citations