Lecture 8:
Expert system shells
Building expert systems
If one wishes to build an expert system,
one has several choices of software
(1) conventional programming
languages (e.g. Pascal, C++, Java)
(2) artificial intelligence programming
languages (particularly LISP and Prolog)
(3) expert system shells
Building expert systems
 The
first choice is almost certainly a bad
 Conventional programming languages
are not designed for this sort of job, and
too much work is required to make the
program perform in the way required.
 However, if it is important to have highly
efficient software, this might be a
suitable choice.
Building expert systems
Choice (2) has the advantage:
flexible system can be built, accurately
reflecting the peculiarities of the knowledge
domain and system task.
 and
the disadvantages:
 Programming
skills in these languages are
not common. It may be necessary to hire
specialist programmers, or retrain the
programming staff.
 Programming the system will always be a
larger (and hence longer and more
expensive) task than using a shell.
Building expert systems
Choice (3) has been the most frequent
choice for commercial systems in recent
Building expert systems
You will remember that an expert system
shell is a ready-made expert system,
with the knowledgebase missing,
together with instructions for building a
knowledgebase in the customer's
chosen domain.
The idea of an e.s. shell
on blood
The idea of an e.s. shell
on chest
The idea of an e.s. shell
on skin diseases
Some organisations avoid using shells
for building complete expert systems;
but even they frequently use them for
 training
 building
Expert system programming
Some people make a distinction
between e.s.shells and
e.s.programming environments (or
"hybrid systems"). For instance, Efraim
Turban does in his book (Turban, 1992).
Expert system programming
Historically, this has been important
because, in the 1980s, most expert
systems projects in the UK used shells
(as described below), and most expert
systems projects in the USA used
Expert system programming
Environments were so called because they
provided several different forms of
knowledge representation, for instance,
 rules
 metarules
 frames
 semantic
and several different forms of inference, e.g.
 forward
 backward chaining
 bidirectional chaining
 non-monotonic reasoning
Expert system programming
They needed more powerful hardware
than a microcomputer - usually, a
Historically, e.s. shells have been more
constrained, perhaps offering only a
single kind of knowledge representation.
They would usually be designed to run
on a PC.
Expert system programming
However, in recent years,
E.S.shells have become more
sophisticated, and added multiple forms
of knowledge representation and of
inference strategy.
PCs have become more powerful, and
PC versions of e.s.environment software
have been released.
Expert system programming
It is probably not useful to make the
distinction any more. One could simply
speak of "simple shells" and
"sophisticated shells".
Advantages and disadvantages of
expert system shells
The programming effort that has gone
into building the user interface and
inference engine is re-used.
Using a shell: advantages
 The level of programming skill needed to
produce the finished system is much
lower than it would be if the system was
programmed from scratch using a
 This means that, if an appropriate shell
is chosen, the project can be completed
faster, and cheaper.
Using a shell: disadvantages
e.s.tools are "end-user tools". Compared
with systems programmed from a
language, such software packages tend
to produce systems that have
 poor documentation
 weak security
 difficult maintenance problems
Using a shell: disadvantages
the problem of flexibility
 If
the shell is a poor match for the type of
knowledge in the domain concerned, it is
liable to produce a system which simply
doesn't correspond to the expertise of the
original domain expert;
Using a shell: disadvantages
In an attempt to model a non-standard
piece of reasoning, the system builders
may produce a "system" which consists
of two or more expert system shells side
by side. Such a "system" is bound to be
unsatisfactory, and to lead to problems
of use, maintenance and training.
The problem of flexibility
The principle underlying the expert
system shell is that a knowledgebase
can be removed from an expert system,
another can replace it, and the system
will reason just as effectively with the
new knowledge as with the old.
The problem of flexibility
This assumes that the same inferencing
techniques are used by every expert,
and in every domain.
The problem of flexibility
In fact, there is evidence that
 Different
experts use different problemsolving skills;
 Different
types of problem-solving task
require different types of reasoning.
The problem of flexibility
"...it must be established that the logic and
reasoning method incorporated in the
shell correspond to those used by the
human expert in problem solving,
otherwise the project is almost certainly
doomed to failure."
Ian Graham, in Forsyth (1989), p.81
Factors involved in choosing a shell, or
other software tool, for an e.s. project
1. The characteristics of the knowledge,
and the style of inference, used by the
domain expert or experts.
2. The time and money available for the
3. The programming capabilities
available in-house (what languages do
the programmers know? Is it feasible to
retrain them?).
Factors involved in choosing a shell, or
other software tool, for an e.s. project
4. The hardware available for
5. The hardware the system will
eventually run on.
6. The required performance of the
Factors involved in choosing a shell, or
other software tool, for an e.s. project
The selection procedure should involve:
a) Doing enough knowledge acquisition
to establish (1).
b) Deciding whether shells are available
whose inference strategies and
knowledge representation match the
requirements of the problem. If not, is
the skill available to treat this as a job for
programming in a computer language?
Factors involved in choosing a shell, or
other software tool, for an e.s. project
c) Establishing that software suggested
by stage (b) will run on the available
hardware, and provide adequate
performance in terms of speed, etc.
d) Establishing that sufficient time and
money is available for the project.
Factors involved in choosing a shell, or
other software tool, for an e.s. project
e) Establishing that any shell still under
consideration has the capabilities
required by the project.
Has it got adequate explanation facilities?
 Can it handle a large enough
 Can it interface easily with other pieces of
software which are to be used by the
finished system?
Factors involved in choosing a shell, or
other software tool, for an e.s. project
These questions should decide whether
the project is viable at all and, if it is,
which shell, or AI language, or
conventional language, is the
appropriate tool for the job.
Example of an up-to-date PC
shell: Acquire SDK
Acquire SDK is marketed by a Canadian
software house (Acquired Intelligence
Inc) as one of a range of expert system
The knowledge-representation involves
objects (as used in object-orientated
programming; these are conceptually
very similar to frames) combined with
rule-based reasoning.
Example of an up-to-date PC
shell: Acquire SDK
Product description, and testimonials,
taken from their web site (Nov.2001):
Example of an up-to-date PC
shell: Acquire SDK
“The Acquire Software Development Kit
(SDK) lets you integrate the Acquire
inference engine and knowledge bases
into your applications. You can build
intelligent applications using many popular
development environments -- including
Visual Basic, Visual C++, Java, Delphi,
PowerBuilder, ToolBook -- or any other
development environment that supports
ActiveX controls or DLL function calls.”
Example of an up-to-date PC
shell: Acquire SDK
“Acquire SDK 2.1 lets you operate multiple
knowledge bases simultaneously within a
single application, and lets many users
access the same knowledge base at the
same time.
Under special arrangements, the Acquire SDK
libraries are available for SCO Unix, Sun
OS, Solaris, and Linux, and can be ported to
almost any Unix variant.”
Example of an up-to-date PC
shell: Acquire SDK
“ Easy to use -- you can build a fullfeatured intelligent application in Visual
Basic with just a handful of statements.
The inference engine generates events
when a rule fires, when a conflict occurs, or
when it needs additional information.
Ability to utilize multiple knowledge bases
simultaneously in one application.
Ability to deliver client/server
Example of an up-to-date PC
shell: Acquire SDK
Includes sample applications that
show you how to build WWW
applications with CGI or Java.
Ability to access the contents of
knowledge bases, including messages
written by the knowledge base author
that can be used to give situationspecific commands to your application,
and permitting customization from within
the knowledge base.”
Example of an up-to-date PC
shell: Acquire SDK
Flexibility of data source: obtain input
interactively from the user, from the
knowledge base, from a database or
spreadsheet, or from a hardware device
or other source.
The expert system is embedded - the
user needn't be aware that an expert
system is being used at all.”
Example of an up-to-date PC
shell: Acquire SDK
“When we first discussed the possibility of
an expert system in neuropsychology, I
thought it was an interesting, albeit
impossible idea. Now that I have used
ACQUIRE® to build two different
knowledge bases (in neuropsychology
and school psychology) I am looking
forward to building other applications for
my clinical practice.”
Dr. Diane Russell, Neuropsychologist
Example of an up-to-date PC
shell: Acquire SDK
“Radio interference is a complex,
diagnostic problem that all countries
have. Using ACQUIRE® has allowed us
to build a huge, comprehensive and
complex knowledge base (The Radio
Interference Advisor) that is so well
structured that it is very easy to
understand, use and maintain. It usually
takes up to three years to teach a new
technician to be a radio inspector.
Example of an up-to-date PC
shell: Acquire SDK
Once trained as a radio inspector, solving
particularly difficult radio interference
problems (e.g., intermodulation
products) can still be very labour
intensive. We are using this as a tool to
speed up both the training process and
the diagnostic process. It is an
extraordinary learning tool, so it can also
be used in the classroom.
Example of an up-to-date PC
shell: Acquire SDK
We've been finding new applications for
the software even before it's finished.”
Dave Sinclair
Operations Manager, Spectrum
Industry Canada (Retired)
Example of an up-to-date PC
shell: Acquire SDK
“MacMillan Bloedel is using the powers of
ACQUIRE® to assist personnel in
machine startup and to help diagnose
machine breakdown. One of the
greatest strengths of this product is that
it is designed for the expert to build
his/her own knowledge base.
Example of an up-to-date PC
shell: Acquire SDK
Bypassing the requirement of a
knowledge engineer can significantly
reduce the project costs and lower the
risk of misinterpreted information. In
addition, ACQUIRE® operates on a PC
platform, eliminating the need to
purchase specialized computer
Sharlene Yap
Computer Scientist, Wood Harvesting
Example of an up-to-date PC
shell: Acquire SDK
“The ACQUIRE® knowledge acquisition
system is the underlying technology for
an intelligent tutoring system for crew
training. The resultant system,
ACQUIRE®ITS, inherits the benefits of
ACQUIRE® while providing the tools
with which the general PC user can
develop and maintain their own
intelligent tutoring applications.”
Canadian Space Agency
Example of an up-to-date PC
shell: Acquire SDK
“Analysing international trade in
commodities and forecasting market
prices are particularly difficult tasks.
Each market differs considerably, and
the trader or analyst must develop
detailed knowledge of his/her specialist
area. Mathematical modeling is often
unsuccessful because it fails to
represent this knowledge adequately,
especially that relating to the
Example of an up-to-date PC
shell: Acquire SDK
nonquantitative factors which affect
commodity markets. ACQUIRE®
allowed us to rapidly model an important
and complex commodity market (for
Soybeans), paying attention to the
psychological elements of "market
sentiment". The resulting system,
SoyTrader, incorporates a number of
rules which make it a considerable
advance on other formal models of this
Example of an up-to-date PC
shell: Acquire SDK
market. ACQUIRE® allowed us to
prototype SoyTrader quickly, and to
achieve impressive forecasting results;
results which other analysts had
doubted were possible.”
Geoffrey Bastin
Economist, MIL, London, U.K.
One piece of knowledge represented in
three rule-based shells.
Original knowledge, elicited from the
domain expert (a salesman for life
assurance products):
"Suppose the customer has a lump sum to
invest, and they want to see some
growth in the investment. Suppose also
that they do want a pension, but don't
need life cover. In that case, I'd advise
them to buy an annuity.”
Example: Crystal
This knowledge represented in Crystal:
IF lump sum to invest
growth desirable
pension needed
NOT life cover needed
AND: conclusion display
Example: Leonardo
This knowledge represented in Leonardo:
1:if investment is 'lump sum'
2:and growth is desirable
3:and pension is desirable
4:and life.cover is unnecessary
5:then advice is annuity
Example: Leonardo
Object number: 2g
1:Name: investment
4:Default value:
5:Allowed value: regular, lump sum
6:Compute value:
7:Query prompt: What kind of payment
are you prepared to make?
Example: Leonardo
8:Query preface:
We have to establish first whether you
wish to save regularly or merely invest a
single lump sum. Later we may explore
a combined approach.
- NB there are 18 slots in an object
Example: Guru
This knowledge represented in Guru:
IF: INVESTMENT = "lump sum" AND
GROWTH = "desirable"
AND PENSION = "desirable" AND
LIFECOVER = "unnecessary"
THEN: ADVICE = "annuity"
Example: Guru
REASON: For someone who wants
capital growth and a pension but has no
need of life cover, the best use of a lump
sum is the purchase of a deferred

Introduction to knowledge