nD-SQL: A Multi-Dimensional Language for Interoperability and OLAP

We propose a multi-dimensional language called nD-SQL with the following features: (i) nD-SQL supports queries that interoperate amongst multiple relational sources with heterogeneous schemas, including RDBMS and relational data marts, overcoming the mismatch between data and schema; (ii) it supports complex forms of restructuring that permit the visualization of ndimensional data using the three physical dimensions of the relational model, viz., row, column, and relation; (iii) it captures sophisticated aggregations involving multiple granularities, to an arbitrary degree of resolution compared to CUBE, ROLLUP, and DRILLDOWN. We propose a formal model for a federation of relational sources and illustrate nD-SQL against it. We propose an extension to relational algebra, called restructuring relational algebra (RRA), capable of restructuring and aggregation. We propose an architecture for the implementation of an nD-SqL server, based on translating nD-SC/L queries into equivalent RRA expressions, which are then optimized. We are currently implementing an nD-SQL server on the PC platform based on these ideas.