Ludwig-Maximilians-Universität München, Institut für Informatik
Technical Report 93-25
- TITLE:
-
Query Translation of an Object-Oriented into a Relational Query Language
- DATE:
-
December 1993
- AUTHORS:
- Daniel A. Keim
- Hans-Peter Kriegel
- Andreas Miethsam
- Institut für Informatik
- Universität München
- Leopoldstr. 11B
- D-80802 München (Germany)
- KEYWORDS:
-
query translation, query languages, relational database
systems, object-oriented database systems, multidatabase
systems, schema enrichment and transformation
- ABSTRACT:
-
In this paper, we present a query translation algorithm which allows
object-oriented queries to be automatically translated into a relational
query language. Our goal is to provide an improved query interface for
existing relational database systems. The translation algorithm, we
propose in this paper may be used to directly access relational databases,
but it may also be useful in the context of object-oriented multidatabase
systems to translate the common global query language into the query
languages of participating relational databases. Necessary steps in
providing object-oriented access to relational databases are schema
enrichment and transformation as well as query translation. The main focus
of this paper is the query translation which has to be performed fully
automatically since it has to be done each time, a query is processed by
the system, whereas schema enrichment and transformation may be done only
once in the beginning. Our query translation algorithm ensures a
full automatic translation of object-oriented queries into equivalent
SQL queries for the original relational schema in all cases where a direct
translation is possible. In all other cases, it generates SQL queries providing a superset of the desired data and a sequence of `formatting'
functions that transform the data into the desired result. Problems may
occur if additional user defined functions are used.
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Robert Stabl
(28.11.1994)