|
In an active database system, rules are used to monitor and
respond to events happened inside the database. That is, rules
are tested actively. Triggers and alerters are such kinds of
rules. A trigger is used to detect some conditions happened in
a database and then react to the database. An alerter is used
to monitor a database and then report the changes to users. The
essential research in an active database is to design a user-
friendly rule language to specify events happened inside the
database, and a rule manager to efficient store, manager and
test rules. The thesis presents the implementation of an active
database system called RBE (Rule-By-Examples). This system,
without designing from scratch, loosely couples OPS5 production
system and IBM INGRES DataBase Management System (noted as
DBMS) to efficiently monitors databases on complex conditions.
In this system, a table-based Rule-By-Examples language(also
called RBE) is designed. The internal representations of the
RBE rule language are production rules; therefore, rules can be
stored, managed, and tested efficiently by using the RETE
pattern matching algorithm in a production system. An interface
(written in C) is used to loosely couple OPS5 rule system with
INGRES DBMS. This interface accepts user's query, inserts this
event into OPS5 rule system to wake up rules and sends the
original query with these derived queries to INGRES DBMS.
Moreover, before those queries are sent to the INGRES DBMS, the
interface will reorder those queries according to their
relationship and assigned priority. The architecture used in
this system shows the applicability of constructing an active
database system by integrating any production system and any
database system.
|