SchemaSQL -- A Language for Interoperability in Relational Multi-database Systems

Abstract

We provide a principled extension of SQL, called SchemaSQL , that offers the capability of uniform manipulation of data and meta-data in relational multi-database systems. We develop a precise syntax and semantics of SchemaSQL in a manner that extends traditional SQL syntax and semantics, and demonstrate the following. (1) SchemaSQL retains the flavour of SQL while supporting querying of both data and meta-data. (2) It can be used to represent data in a database in a structure substantially different from original database, in which data and meta-data may be interchanged. (3) It also permits the creation of views whose schema is dynamically dependent on the contents of the input instance. (4) While aggregation in SQL is restricted to values occurring in one column at a time, SchemaSQL permits "horizontal" aggregation and even aggregation over more general "blocks" of information. (5) SchemaSQL provides a great facility for interoperability and data/meta-data manage..