Database and Expert Systems Integration - Information Systems Reengineering, Integration and Normalization - page 310

Tier 4: Application Development
After the integrated system has been developed, the system developer can use it as
a knowledge base to develop its own application. The application system defines
the components necessary to answer and give explanations for all problems that it
is to solve.

8.2 A Knowledge-Based Model for the Integration of

Expert Systems and Database Systems

An expert system frame model metadata (Huang 1994 ) is a good example of a
knowledge-based model that fulfils the requirements for constructing an integrated
EDS. The frame model metadata is an EER model framework used to construct an
effective knowledge-based management system. It is a higher-order synthesis that
includes frame concepts, semantic data modeling concepts and object-oriented con-
cepts to ensure no real distinction between “data” and “knowledge.”
The frame model metadata is an object-oriented-like database that structures an
application domain into classes. Classes are organized via generalization, aggrega-
tion, and user-defined relationships. Knowledge-based system designers can de-
scribe each class as a specialization (i.e., subclass) of its more generic superclass(es).
Thus, attributes and methods of objects of one class are inherited by attributes and
methods of another class lower in the ordering.
The ability to attach procedures to objects enables behavior models of objects
and expertise in an application domain to be encapsulated in a single construct. The
attached procedures follows an IF-THEN structure that enables representation of
production rules as well as normal procedures.
The constraints of database systems include integrity constraint enforcement,
derived data maintenance, triggers, protection, version control, and so on. These
are referred to as active database and deductive database systems. The frame model
metadata unifies data and rules allowing these advanced features to be implement-
ed. The knowledge processing mechanism (i.e., inference engine) and data retrieval
mechanisms, have also been built into the frame model metadata. It also supports
very strong integrity constraint enforcement.
The frame model metadata follows the object-oriented paradigm. All conceptual
entities are modeled as objects. The same attribute and behavior objects are classi-
fied into an object type, called a class. An object belongs to one, and only one, class.
Both facts and rules are objects in the frame model metadata.
The frame model metadata is implemented with a knowledge representation
schema that includes object structure descriptions (i.e., classes), user-defined rela-
tionships between entities, and structure inheritance descriptions defined by taxono-
mies of structure that support data and behavior inheritance (i.e., abstract relation-
ship) as shown in Fig. 8.2 .