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Unit 13: Expert System Architecture

Scalability Notes

Evolving an expert system is to add, modify or delete rules. Since the rules are written in plain
language, it is easy to identify those to be removed or modified.

Pedagogy

The engines that are run by a true logic are able to explain to the user in plain language why they
ask a question and how they arrived at each deduction. In doing so, they show knowledge of the
expert contained in the expert system. So, user can learn this knowledge in its context. Moreover,
they can communicate their deductions step by step. So, the user has information about their
problem even before the final answer of the expert system.

Preservation and Improvement of Knowledge

Valuable knowledge can disappear with the death, resignation or retirement of an expert.
Recorded in an expert system, it becomes eternal. To develop an expert system is to interview an
expert and make the system aware of their knowledge. In doing so, it reflects and enhances it.

New Areas Neglected by Conventional Computing

Automating a vast knowledge, the developer may meet a classic problem: “combinatorial
explosion” commonly known as “information overload” that greatly complicates his work and
results in a complex and time consuming program. The reasoning expert system does not
encounter that problem since the engine automatically loads combinatorics between rules. This
ability can address areas where combinatorics are enormous: highly interactive or conversational
applications, fault diagnosis, decision support in complex systems, educational software, logic
simulation of machines or systems, constantly changing software.

13.6.1 Utility of Expert Systems

Expert systems are especially important to organizations that rely on people who possess
specialized knowledge of some problem domain, especially if this knowledge and experience
cannot be easily transferred. Artificial intelligence methods and techniques have been applied
to a broad range of problems and disciplines, some of which are esoteric and others which are
extremely practical. One of the early applications, MYCIN, was created to help physicians diagnose
and treat bacterial infections. Expert systems have been used to analyze geophysical data in our
search for petroleum and metal deposits (e.g., PROSPECTOR). They are used by the investments,
banking, and telecommunications industries. They are essential in robotics, natural language
processing, theorem proving, and the intelligent retrieval of information from databases. They
are used in many other human endeavors which might be considered more practical.

Notes Rule-based systems have been used to monitor and control traffic, to aid in the
development of flight systems, and by the federal government to prepare budgets.
A rule-based, expert system maintains a separation between its Knowledge-base and that part of
the system that executes rules, often referred to as the expert system shell. The system shell is
indifferent to the rules it executes. This is an important distinction, because it means that the
expert system shell can be applied to many different problem domains with little or no change.

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