ERIC Identifier: ED335058
Publication Date: 1991-06-00
Author: Boss, Richard W.
Source: ERIC Clearinghouse on Information Resources Syracuse
What Is An Expert System? ERIC Digest.
Expert systems are computerized tools designed to enhance the quality
and availability of knowledge required by decision makers in a wide range
of industries. They augment conventional programs such as databases, word
processors, and spreadsheet analysis.
Expert systems differ from conventional applications software in the
o The expert system shell, or interpreter.
o The existence of a "knowledge base," or system of related concepts
that enable the computer to approximate human judgment.
o The sophistication of the user interface.
THE EXPERT SYSTEM SHELL
While any conventional programming language can be used to build a knowledge
base, the expert system shell simplifies the process of creating a knowledge
base. It is the shell that actually processes the information entered by
a user; relates it to the concepts contained in the knowledge base; and
provides an assessment or solution for a particular problem. Thus, an expert
system shell provides a layer between the user interface and computer operating
system to manage the input and output of data. It also manipulates the
information provided by the user in conjunction with the knowledge base
to arrive at a particular conclusion. The structure of the shell is very
similar to that of an interpreter or a front-end to a database program.
The shell also manages the user interface, performing functions that range
from the validation of numeric values entered on the screen to management
of the mouse and the representation of graphical objects.
The shell is often sold as an end-product, allowing the purchaser to
encode a knowledge base from scratch the same way a user would purchase
a database management system. On the other hand, knowledge bases can be
sold as products--where a shell or interpreter may be an incidental part
of the package--in the same way a user might buy data.
THE KNOWLEDGE BASE
The main purpose of the knowledge base is to provide the guts of the
expert system--the connections between ideas, concepts, and statistical
probabilities that allow the reasoning part of the system to perform an
accurate evaluation of a potential problem. Knowledge bases are traditionally
described as large systems of "if then" statements, but this description
is misleading because knowledge bases may not contain definitive rules
at all, but may contain only associative relationships among different
concepts, statistical information about the probability of certain solutions,
or simply large databases of facts that can be compared to one another
based on simple conventions intrinsic to the expert system.
THE USER INTERFACE
For the last several years, interface designs for expert systems have
hinged on graphical capabilities and unconventional methods of entering
data into the system. For example, many expert systems used a mouse for
data entry well before the Macintosh became popular. Graphical interfaces
can supply information in any number of forms: simple text "dressed up"
in windows, pop-up menus, or actual graphical objects. Recently, many of
those formats have been integrated into conventional applications, but
they are of particular use in expert systems. An expert system may express
an idea, solution, or explanation using more complex conventions than rows
of numbers, pie charts, or brief messages.
THE OPERATING SYSTEM
The computer's operating system plays an important role in the implementation
of an expert system. The operating system provides the basic capabilities
of the machine to the expert system, including file management, some user
interface support, memory management, and interfaces to other products
that might be wanted to share information that is contained in the expert
system. The operating system's resources and utilities may intrinsically
provide needed capabilities (for example, graphic or mouse support and
database management) that, therefore, ease the need for additional programming.
In some cases, the operating system may even provide conventions for interfacing
the expert system to other programs. The disadvantage of using the operating
system's facilities is the limited control the developer has over the facilities
and likely performance degradation. For example, in the PC environment,
OS/2 and Presentation Manager provide much better interface support than
The purpose of the expert system is to enhance judgment on the part
of the user, not to replace human judgment altogether. Expert systems can
provide a relatively inexperienced user with a lucid assessment of a problem
where an expert is unavailable.
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Reprinted with permission of the American Library Association, from
LIBRARY SYSTEMS NEWSLETTER, "What is an Expert System?" Vol. IX, Number
7, July 1989, (c) ALA.