An intermediate database language and its rule-based transformation to different database languages

摘要

A user or a comptuter system which extracts information from heterogeneous DBMSs faces the hard problem of dealing with different target database languages for each DBMS. We propose a solution for this problem based on an intermediate database language and its rule-based transformation to target languages. This solution is implemented in the database access module of the Intelligent Database Assistant, developed at GTE Laboratories.We describe the intermediate database language GTE DELPHI, which combines the power of relational algebra with practically important database operations, including output to a file, grouping, aggregate computations, and nested queries. We show how to convert GTE DELPHI to different relational and 4th generation database languages by a rule-based transformation system and indicate how a conversion program can be generated from examples. Translation from a high-level user language (such as English) to GTE DELPHI is simplified by using a universal relation version of GTE DELPHI as an intermediate step.