CDOL: A Comprehensive Declarative Object Language
Susan D. Urban, Anton P. Karadimce, Suzanne W. Dietrich,
Taoufik Ben Abdellatif, Hon Wai Rene Chan
Department of Computer Science and Engineering
Arizona State University
Tempe, AZ 85287-5406
{s.urban$|$s.dietrich}@asu.edu
Abstract
In this paper we present a rule-based database language known as
CDOL (Comprehensive, Declarative Object Language)
that is an integration of deductive, object-oriented,
and active database technology. CDOL provides sublanguages for the
expression of derived data, constraints, updates, and
active rules.
The rule-based query language of CDOL provides an expressive
approach to extend the stored database with derived attributes and classes.
The constraint sublanguage allows explicit
declarative specification of integrity constraints as a basis
for database consistency. The
update sublanguage of CDOL enables ad-hoc declarative update
requests, where updates are encapsulated in the methods associated with class definitions, thus conforming to traditional object-oriented design concepts. The active
rule sublanguage provides active, user-transparent
agents that support reactive behavior within CDOL applications. In particular,
active rules can be used to supplement declarative updates to maintain
database consistency with respect to the set of integrity constraints. Active
rules in general are used to monitor the occurrence of specific events and to serve as alerters and triggers within a CDOL application. This paper presents
the rule-based query language of CDOL and illustrates the manner in which the
constraint, update, and active rule sublanguages build on this declarative framework. The use of methods and transactions are also
addressed, together with a discussion of the semantics of active rule processing.
Keywords: Object-oriented databases, active rules, deductive rules,
derived data, constraints, updates, rule-based query language.