Design and Implementation of Reeective Sql Extended Abstract

One weakness of SQL has been its inability to express certain classes of queries, e.g., iterative queries and database schema-independent queries. Fixes to this problem generally involve embedding SQL in a more expressive language. Re ection|the ability of a language to encode arbitrary programs and evaluate these encodings during execution|can provide a seamless, natural solution. In database query languages re ection has been generally con ned to a procedural setting, where one paper in particular, Van den Bussche et al, has given us much of our inspiration; however, exactly how to pragmatically incorporate re ection into a query language like SQL has remained elusive. This paper presents the design and implementation of a Re ective SQL (RSQL): an extension of SQL wherein programs themselves can create (i.e., reify), manipulate and evaluate programs. Ordinary SQL tables serve to encode these programs; these tables look and feel much like the programs they encode and, furthermore, retain SQL's declarative nature. The implementation itself is comprised of an RSQL interface and a relational database server. This work establishes, in a practical setting, a means of enhancing SQL, opening new avenues to solutions of database problems that have been hitherto inaccessible through SQL alone. Computer Science Dept., Indiana University, Bloomington, IN 47405, USA. Email: fdalkilic,mjain,[email protected] yXerox Palo Alto Research Center, 3333 Coyote Hill Road, Palo Alto, CA 94304, USA. Email: [email protected]