A Gateway from DBPL to Ingres

A gateway from DBPL (being a superset of Modula-2) to the commercial database system Ingres is described. DBPL extends Modula-2 by a new bulk data type constructor \relation", persistence, and high-level relational expressions (queries) based on the predicate calculus, thereby maintaining the basic concepts of the language like strong typing and orthogonality. The gateway enables the user to write normal DBPL programs for accessing Ingres databases. This is in contrast to typical implementations that embed SQL statements into a programming language and results in a fully transparent interface for DBPL programmers. DBPL queries and statements referring to Ingres tables are automatically converted into corresponding SQL statements, are evaluated by the Ingres database server and the results are transferred back under the control of the DBPL program. This procedure also resolves queries referring to both Ingres and DBPL tables. The design assumptions of the gateway and the used implementation methods are presented as well as design and implementation diiculties.