EXTENDING SQL-92 FOR OODB ACCESS - DESIGN AND IMPLEMENTATION EXPERIENCE

This paper describes the design and implementation of a query engine t hat provides extended SQL-based access to the data managed by an objec t-oriented database system. This query engine allows extended SQL quer ies to be embedded in C++ programs or issued interactively from a comm and line interface. The language supported by the engine is the comple te SQL-92 select statement plus object extensions for navigating along paths and embedded structures, querying nested sets, and invoking mem ber functions. In addition, an object-oriented SQL view facility is pr ovided. Using this view facility, one can define object-oriented views ; one can also define views that flatten complex OODB schemas, allowin g direct access by existing tools designed to provide remote access to relational databases. The view facility also supports the definition of views that include reference and set-valued columns based on other views, thus allowing entire ''view schemas'' to be created. This paper describes the SQL-92 query and view extensions and discusses a number of issues that arose on the way to the implementation that is current ly running on top of the ObjectStore OODB system.