文档介绍：Description Logics for Semantic Query
Optimization in Object-Oriented
Database Systems
DOMENICO BENEVENTANO and SONIA BERGAMASCHI
Universit`a di Modena e Reggio Emilia and R
and
CLAUDIO SARTORI
Universit`a di Bologna and R
Semantic query optimization uses semantic knowledge (., integrity constraints) to transform a
query into an equivalent one that may be answered more efficiently. This article proposes a general
method for semantic query optimization in the framework of Object-Oriented Database Systems.
The method is effective for a large class of queries, including conjunctive recursive queries ex-
pressed with regular path expressions and is based on three ingredients. The first is a Description
Logic, ODLRE, providing a type system capable of expressing: class descriptions, queries, views, in-
tegrity constraint rules and inference techniques, such as incoherence detection and subsumption
computation. The second is a semantic expansion function for queries, which incorporates restric-
tions logically implied by the query and the schema (classes + rules) in one query. The third is an
optimal rewriting method of a query with respect to the schema classes that rewrites a query into
an equivalent one, by determining more specialized classes to be accessed and by reducing the num-
ber of factors. We implemented the method in a tool providing an pliant interface that
allows a full interaction with OQL queries, wrapping underlying Description Logic representation
and techniques to the user.
Categories and Subject Descriptors: [Database Management]: Languages—query lan-
guages; [Database Management]: Systems—object-oriented databases; query processing
General Terms: Algorithms, Management, Languages, Theory
Additional Key Words and Phrases: Semantic query optimization, query rewriting method,
integrity constraints rules, semantic expansion of a query, description logics, subsumption
This research was partially funded by the Italia