EXSYS Professional Developer Interface

Expert System Software 

THE EXSYS 

® 

DE V E L O P E R 

OV E RV I E W 

SELECTING THE RIGHT TOOL 

FOR THE RIGHT PROJECT 

How To Get Systems Built 

FUZZY LOGIC TO REPORT GENERATION - 

FEATURES TO GET SYSTEMS BUILT FAST 

Terminology and the Developer Interface 

INTEGRATE EXPERT SYSTEM DECISION-MAKING 

INTO EXISTING SYSTEMS 

I n t e rfaces and Embeddability

T 

ABLE OF CONTENTS 

When to Use an Expert System 1 

How Does an Expert System 

Get Developed 2 

EXSYS RULEBOOK 2 

EXSYS RULEBOOKPLUS 2 

EXSYS PROFESSIONAL 2 

EXSYS LINKABLE OBJECT MODULES 2 

The EXSYS Professional Terminology and 

Inference Engine 2 

EXSYS Rules 2 

EXSYS DATA ELEMENTS 3 

BACKWARD CHAINING 3 

FORWARD CHAINING 4 

PROCEDURAL COMMAND LANGUAGE 4 

CONFIDENCE MODES 5 

YES/NO SYSTEM 5 

0-10 SYSTEM 5 

-100 TO 100 SYSTEM 5 

INCREMENT/DECREMENT SYSTEM 6 

CUSTOM FORMULA SYSTEM 6 

FUZZY LOGIC 6 

EXSYS PROFESSIONAL FRAMES 6 

EXSYS PROFESSIONAL BLACKBOARDS 6 

PARAMETER REPLACEMENT 6 

The EXSYS RuleBook Developer Interface 6 

TREES 7 

NODES 7 

FACTORS 7 

VARIABLES 8 

CHOICES 8 

BALLOONS 8 

ADDING NODES TO A TREE 8 

THE RULEBOOK EXPERT 10 

RULEBOOK - THE BOTTOM LINE 10 

EXSYS RuleBook PLUS 11 

EXSYS Professional Developer Interface 11 

EXSYS PROFESSIONAL RULE EDITOR 11 

CONFIGURATION OPTIONS 11 

The Developer Overview 

FUZZY LOGIC 12 

HO W FU Z Z Y LO G I C I S IM P L E M E N T E D I N 

EXSYS PR O F E S S I O N A L 13 

DEFUZZIFICATION 14 

ADVANTAGE OF FUZZY SETS 15 

DE B U G G I N G 15 

EXSYS PROFESSIONAL AUTOMATIC SYSTEM 

VALIDATION AND TREE DIAGRAMS 15 

VALIDATION GRAPHS 16 

EXSYS PROFESSIONAL RULE COMPILER 17 

EXSYS REPORT GENERATOR 17 

EXSYS End User Interface 17 

EXSYS PROFESSIONAL CUSTOM SCREENS 17 

EXSYS EXDESIGN CUSTOM SCREEN 18 

DESIGN PROGRAM 

SCREEN TEMPLATES 19 

CUSTOM HELP 19 

HYPERTEXT 19 

WHY AND HOW 19 

CHANGE AND RERUN 19 

TEXT EXPLANATION 19 

UNDO 19 

REPORT GENERATOR 19 

HISTORY 19 

INTEGRATION 19 

DDE LINKS 20 

EMBEDDABILITY 20 

EXSYS Professional Linkable 

Object Modules 20 

Interfaces 21 

DATABASES 21 

SPREADSHEETS 22 

LINEAR PROGRAMMING 22 

EXSYS/LINDO SYNTAX 22 

MODEL COMMANDS 22 

CONDITIONAL INCLUSION OF LINES 22 

DATA COMMANDS 23 

NEURAL NET INTERFACE 23 

EXSYS/PI INTERFACE 24 

OTHER PROGRAMS 24 

EXSYS Company History 25 

EXSYS Contact Information 25

E 

xpert knowledge is often scarce and valuable. 

Expert systems are computer programs that 

capture some of that knowledge and allow its 

dissemination to others. 

An Expert System is a program that emulates the 

interaction a user might have with a human expert to solve 

a problem. The end user provides input by selecting one or 

more answers from a list or by entering data. The program 

will ask questions until it has reached a conclusion. The 

conclusion may be the selection of a single solution or a 

list of possible solutions arranged in order of likelihood. 

The program can explain, in English, how it arrived at its 

conclusion and why. 

Many expert systems are not complex or difficult to build. 

In a very simple case, consider a tree diagram on paper 

describing how to solve a problem. By making a selection 

at each branch point, the tree diagram can help someone 

make a decision. In a sense, it is a very simple expert 

system. This type of tree structured logic can easily be 

converted to a computerized system that is easier to use, 

faster and automated. More elaborate systems may 

include confidence factors allowing several possible 

solutions to be selected with different degrees of 

confidence. Expert systems can explain why data is 

needed and how conclusions were reached. A system 

may be highly interactive (directly asking the user 

questions) or embedded where all input comes from 

another program. 

The range of problems that can be handled by expert 

systems is vast. Expert systems can be developed with 

EXSYS software for any problem that involves a selection 

from among a definable group of choices where the 

decision is based on logical steps. Any area where a 

person or group has special expertise needed by others is a 

possible area for EXSYS. Expert systems can help 

automate anything from complex regulations to aiding 

customers in selecting from among a group of products, or 

diagnosing equipment problems. 

When to Use an Expert System 

The first question in considering the development of an 

expert system is “Why build an expert system” Expert 

systems are very useful, but they can not solve all 

problems. Understanding when and why to use an expert 

system is important. 

EXSYS Expert System Software 

THE 

DE V E L O P E R 

OVERVIEW 

EXPERT SYSTEMS ARE IDEAL TO: 

Disseminate problem-solving knowledge, not just 

facts, with minimal training of end users. 

Most organizations have ways to disseminate data through 

databases and networks. Expert systems provide a way to 

disseminate knowledge through those same networks. 

Once an expert system is built and put on-line, the 

problem solving skill it contains is available to everyone. 

Staff with minimal training can immediately perform at a 

much higher level by using expert systems. 

Standardize the conclusions for a given set of data. 

For situations where there are many people answering the 

same types of questions, it is highly desirable that 

everyone give the same answer for the same input data. 

Expert systems guarantee that this will happen. 

Free a human expert from repetitive, routine jobs in 

order to do activities an expert system cannot do. 

Expert systems are very powerful tools, but they do not 

think. Expert systems can not come to novel or innovative 

solutions - only people can. However, most experts spend 

the majority of their time answering routine, well 

understood, questions. These are the best areas to convert 

to an expert system. This frees the human expert to 

concentrate on the complex problems that can not be done 

by an expert system. 

Codify a problem-solving technique for future users. 

Most organizations have people that are experts on some 

subject, but the expert has never documented how they 

make their decisions. Having the expert build an expert 

system, documents and preserves the steps they use to 

make their decisions. 

Allow the problem-solving skills of several people to 

be combined. 

In addition to documenting the steps a single expert may 

use, having a group of experts build a system will separate 

the consensus opinion from individual views. This can be 

very informative. 

The goal of a particular expert-system project may be a 

combination of several of the above. The best problems to 

attack with expert systems are those that are well 

understood and frequently asked. Typically these problems 

can be rapidly converted into expert systems with 

immediate payback. Building such systems frees the expert 

from the routine questions, allowing them to concentrate on 

the problems that can not be handled by an expert system. 

THE EXSYS DEVELOPER OVERVIEW • 1

Companies effectively using expert systems have found 

that “experts” are much more common in a company than 

it seems at first. The “expert” is the person who knows the 

answers. Many people in a company have specialized 

information needed by others. Whether it is how to fix a 

complex machine, provide answers at a Help Desk, ship a 

package or comply with regulations - usually there is an 

“expert” that everyone turns to. An expert system takes 

the expert’s knowledge and enables it to be preserved and 

disseminated. 

How Does an Expert System 

Get Developed 

Traditionally expert system development has been a major 

expense both in time and money. Getting even a single 

system built was a big project. The cost of system 

development prohibited building expert systems on more 

than a few projects. EXSYS tools change that. The key 

to implementing expert systems widely, effectively and at 

low cost is to make easy-to-use expert system development 

tools readily available to the experts. EXSYS provides a 

multi-level approach to expert system development by 

providing a suite of tools, combining many advanced 

features with the proven ease of the EXSYS development 

interface. This avoids the inefficiency of having to learn 

complex tools to do simple problems. 

EXSYS tools were developed to meet the increasingly 

sophisticated needs of experts building complex expert 

systems. The goal of EXSYS is to balance the often 

conflicting requirements of flexible power and ease-ofuse. 

To do this, EXSYS provides four levels of tools with 

increasing capability allowing developers to use the easiest 

tool that will meet their needs. In addition, the tools are 

designed so that you need only learn a small portion of the 

commands to build most expert systems. 

As more power is needed for certain applications, higher 

level tools can be used with advanced features to give you 

complete control over the inference engine, 

modularization of the knowledge base, flow of execution, 

the user interface and integration with other programs. 

The EXSYS tools are: 

EXSYS RuleBook 

Applications are built by creating tree diagrams of 

decision making logic. A very short learning curve allows 

experts to be rapidly building rules. The trees are 

automatically checked for completeness and for a variety 

of logic errors. The tree diagram approach makes it easy 

for developers to understand the logic without having to 

learn complex syntax. RuleBook applications are often 

built in just a few days. 

EXSYS RuleBook PLUS 

The RuleBook tree diagram approach to building 

applications is also used in RuleBook PLUS. However, 

RuleBook PLUS adds the procedural command language 

of EXSYS Professional enabling it to handle much more 

2 • THE EXSYS DEVELOPER OVERVIEW 

complex logic and control problems. RuleBook PLUS 

also adds many more interfaces, including SQL databases, 

spreadsheets, frames, tables, blackboards and linear 

programming. 

EXSYS Professional 

Applications developed in RuleBook or RuleBook PLUS 

can be moved to EXSYS Professional. This is a rule 

editor where rules can be built and fine tuned one at a 

time, allowing logic that can not be diagrammed as trees 

to be represented. EXSYS Professional also support fuzzy 

logic, procedural commands and a wide variety of 

interfaces. Professional is a little more complex to use than 

RuleBook, but the EXSYS three day training class takes 

novice students through to prototyping their application. 

EXSYS Linkable Object Modules 

The perfect tool for embedded applications and custom 

development. Systems developed with EXSYS Professional 

can be converted to C code. Custom commands and 

interfaces can be added, or the entire application can be 

invisibly embedded inside another program. Linkable 

Object Modules is a C programmers tool, and gives 

unlimited flexibility for complex applications. 

The ease of getting started, combined with the proven 

ability to handle complex problems has made EXSYS 

software the tools of choice by both beginners and 

professional knowledge engineers. 

The EXSYS Terminology and 

Inference Engine 

EXSYS software is a rule-based expert system shell with 

many enhancements such as Frames, Blackboards and the 

Procedural Command Language. IF-THEN-ELSE rules 

are used to describe the logic of the system. The rules 

may be built one at a time in a rule editor (EXSYS 

Professional) or built by converting tree diagram 

representation of the logic (EXSYS RuleBook). 

EXSYS RULES 

Expert systems deal with knowledge rather than data and 

the files they use are often referred to as knowledge bases. 

This knowledge is represented as rules. A rule is made up 

of a list of IF conditions (normal English sentences or 

algebraic expressions that can be tested to be TRUE or 

FALSE) and a list of THEN conditions (more sentences) 

or statements about the probability of a particular data or 

choice being the appropriate solution to the problem. If the 

computer determines that all IF conditions in a rule are 

true it adds the rule’s THEN conditions to what it knows 

to be true. The computer determines what additional 

information it needs and how best to get the information. 

If possible, the program will derive information rather than 

asking the user. This ability to derive information allows 

the program to combine many small pieces of knowledge 

to arrive at logical conclusions about complex problems.

An EXSYS rule is divided into five parts: an IF part, a 

THEN part, an optional ELSE part, an optional NOTE and 

an optional REFERENCE. 

IF 

Conditions 

THEN 

Conditions 

and Choices 

ELSE 

Conditions 

and Choices 

NOTE: —————————— 

REFERENCE: ———————- 

The IF part is simply a series of test conditions, expressed 

as English sentences or algebraic expressions. The test 

conditions are statements which may be true or false. For 

example, TODAY IS WEDNESDAY or [X]>1. The first 

statement will be true only on Wednesdays, the second 

will be true only if the value of the variable X is greater 

than 1. The IF conditions are tested against the data 

provided by the user, information that can be derived from 

other rules, and data obtained from other sources. 

The IF part, THEN part and ELSE part can each have up 

to 128 conditions. In the IF part, the tests can be 

combined with either AND or OR. Boolean operators can 

also be used to build complex logical tests. 

The THEN part can contain conditions similar to the IF 

part, but in the THEN part, they are not tests, but 

statements of fact. In the IF part we could have TODAY 

IS WEDNESDAY and it would be a t e s t that might be true 

or false. The same statement in the THEN part would be 

considered to be a valid fact if the IF conditions in the rule 

were true. When the IF conditions in a rule are determined 

to be true, EXSYS Professional assumes the THEN part is 

true and adds any facts in the THEN conditions to what it 

knows. 

The THEN part can also contain choices (the possible 

goals that the expert system will decide among) along with 

their assigned probability values. EXSYS keeps track of 

the value each choice receives and calculates a final 

confidence value for each of the choices. 

The THEN conditions may also include statements that 

assign a value to a numeric or string variable. This allows 

values to be calculated during a run and, optionally, 

displayed at the end. 

The ELSE part is the same as the THEN part and is 

applied if any of the IF conditions are FALSE. The ELSE 

part is optional and not needed in most rules. (Rules built 

from RuleBook trees only have IF and THEN parts.) 

In some cases it is desirable to add a note to a rule to 

provide some special information to the user. If there is a 

note added, it will be displayed with the rule. The note 

does not affect the logical operation of the program, but is 

very useful to provide information to the end user. The 

notes, from rules that fired, can also be output using the 

report generator. 

The developer of the expert system knowledge base may 

also add a reference for a rule. This is intended to help the 

end user find the source of the knowledge contained 

within a rule or for more information if they should need 

it. As with the note, the reference is optional and only for 

the end user’s information. It has no affect on the running 

of the program. The difference between the note and the 

reference is that the note is displayed whenever the rule is 

displayed. The reference is displayed only if the user 

requests the reference. The references, from rules that 

fired, can also be output using the report generator. 

EXSYS DATA ELEMENTS 

There are two main types of data in EXSYS: qualifiers 

and mathematical variables. 

Qualifiers are multiple choice lists. There can be up to 30 

possible selections in the list. Usually qualifiers are 

constructed so that when one or more items are selected 

from the list, it makes a sentence. For example we might 

have a qualifier with three possible values: 

The color is 

1 red 

2 white 

3 blue 

Qualifiers are used to build the text conditions in rules. If 

the first value was selected, the statement would be “The 

color is red”. In the IF part this would be a test. In the 

THEN part, it would be a statement of fact. 

The other type of expression is based on mathematical 

variables. EXSYS supports both numeric and string 

variables. Variables can have up to 18 character names 

and are indicted by [ ]. When building expressions, 

parenthesis, Boolean operators, trig functions and 

exponential functions are supported. An IF part test 

expression might be: 

IF 

(([X] < [Z]) AND (SIN([X] / 2) > .4)) 

In addition to the more standard mathematical operators, 

EXSYS also support, MIN, MAX, the C language 

conditional assignment operator (__?__:__) and an 

approximately equal operator to handle round-off error 

problems. 

String variables can be tested for alphabetical order and 

can be concatenated. 

BACKWARD CHAINING 

Backward chaining is a term used to describe running the 

rules in a “goal driven” way. In backward chaining, if a 

piece of information is needed, the program will 

automatically check all of the rules to see if there is a rule 

that could provide the needed information. The program 

will then “chain” to this new rule before completing the 


first rule. This new rule may require information that can 

be found in yet another rule. The program will then again 

automatically test this new rule. The logic of why the 

information is needed goes backwards through the chain 

of rules. For example, suppose we have a rule that we are 

testing: 

Rule 1 

IF 

The day is hot 

THEN 

Go to the beach 

The program needs to know if the day is hot. EXSYS 

would automatically check all rules to see if there is a rule 

that tells if the day is hot. Suppose it finds Rule 35: 

Rule 35 

IF 

It is summer 

and It is sunny 

THEN 

The day is hot 

The program will wait to finish testing Rule 1 until it tests 

Rule 35. Rule 1 is now in the chain. If there are any other 

rules that tell the program if it is summer or if it is sunny, 

these rules would be tested before Rule 35, and so on, 

until there are no rules that can add information. Then the 

chain will unwind back to the starting rule. In all EXSYS 

software, backward chaining is used as the default 

(forward chaining is also available). It is NOT necessary 

to specify which rules apply to which information. 

Backward chaining simplifies the development of the 

expert system. Each rule can simply state an individual 

fact. Unlike some expert system tools, you do not have to 

explicitly assign the relationships between rules. EXSYS 

will automatically find the relevant rules and use them. In 

a backward chaining system, the rules can be in any order. 

As new facts are added to the system, rules are simply 

added and EXSYS will automatically determine when and 

how to use the new pieces of information. 

FORWARD CHAINING 

Forward chaining is the alternative to backward chaining. 

Forward chaining is a “data driven” way to run the rules 

(unlike the goal driven approach of backward chaining). 

In backward chaining, there is always a goal to be satisfied 

and a specific reason why rules are tested. In pure forward 

chaining, rules are simply tested in the order they occur 

based on available data. If information is needed, other 

rules are n o t invoked - instead, the user is asked for the 

information. Consequently, forward chaining systems are 

dependent on rule order. However, since time is not spent 

determining if information can be derived, forward 

chaining is much faster. 

EXSYS also provides a hybrid between backward and 

forward chaining where the basic approach is data driven, 


but information needed by rules is derived through 

backward chaining. This system combines the best of 

both worlds. Another technique is to divide an expert 

system into subsets of rules and run some in forward 

chaining and some in backward chaining with the 

Command Language. This enables the you to fine tune 

the chaining methods for the system. 

PROCEDURAL COMMAND LANGUAGE 

The EXSYS Procedural Command Language was 

developed to solve a major problem encountered in rulebased 

systems. When procedural control of a system is 

closely coupled with the logic of the rules, it becomes 

necessary to use artificial logical structures to force 

procedural operations to be performed. This is difficult to 

develop and maintain and can be very confusing to the end 

user. To solve this problem, the logical and procedural 

operations were separated. The EXSYS Procedural 

Command Language allows a purely procedural 

definition of the flow of the system to be stated. This 

removes procedural commands from the rules and allows 

the rules to represent only the logic of the system. The 

procedural and logical operations can communicate, but 

they do not get in each other’s way. Complex systems can 

be built easier and they are easier to maintain and 

understand. EXSYS Professional and EXSYS RuleBook 

PLUS are the only expert system shells that use this 

powerful approach to solve the problem of logical and 

procedural control. 

The Command Language syntax is somewhat like DOS 

batch language plus a little BASIC. The commands use 

syntax that is easy to follow and maintain. 

The Command Language provides control mechanisms for 

the input of data, execution of rule subsets, looping, and 

display of results. Most of the EXSYS Professional 

default operations can be changed through the Command 

Language. The Command Language is used in conjunction 

with the report generator specifications for even greater 

control. The Command Language program is a text file 

that can be created and edited with any text editor, or with 

the special Command File editor built into EXSYS. If the 

command file is present, it is used. If it is not found, 

EXSYS Professional reverts to the standard defaults. 

Like many advanced EXSYS functions, the command file 

need only be created when it is needed. 

The EXSYS Professional Command Language includes 

commands for: 

• Controlling command flow: (WHILE, IF, GOTO, ...). 

• Running rules or subsets of rules in forward or 

backward chaining mode. 

• Calling report specification files. 

• Displaying results or intermediate results. 

• Instantiating facts or data. 

• Screen control to ask questions. 

• Calls to database or spread sheet files. 

• Calls to external programs.

While only a small part of the commands in the language 

can be described here, this short example gives some idea 

of the power and flexibility that can be achieved. This is 

not an actual expert system command file, it is simply a 

collection of commands for illustration purposes. (The 

line numbers are added only for reference, they are not 

part of the Command Language.) 

1 SET [Z] 0 

2 :START_LOOP 

3 RULES [X] /F 

4 IF ([X] > 5) 

5 RULES “PART 1:*” 

6 REPORT “FIRST.RPT” 

7 ELSE 

8 RULES “PART 2:*” 

9 REPORT “SECOND.RPT” 

10 ENDIF 

11 RESULTS 

12 CLEAR ALL 

13 WHILE ([Y] > 0) 

14 RULES 100-200 /C 

15 WEND 

16 IF ([ABC] < 0) 

17 SET [Z] ([Z]+1) 

18 GOTO START_LOOP 

19 ENDIF 

This program would first set EXSYS variable [Z] to 0 

(line 1). Line 2 is a loop branch point. Line 3 would run 

all of the rules that derive a value for variable [X] in a 

forward chaining mode. It would then test the value 

obtained for [X] (line 4). If [X] is greater than 5, the set of 

rules whose name begins with “PART 1:” would be run in 

backward chaining mode (line 5) and the results printed 

using the report specification “FIRST.RPT” (line 6). If 

[X] was not greater than 5, the subset of rules whose 

names begin with “PART 2:” would be run in backward 

chaining mode (line 8) and the report “SECOND.RPT” 

used (line 9). In either case the results would be displayed 

to the user (line 11), all rules, qualifiers, variables and 

choices are reset to unknown (line 12). The program will 

then determine the value of variable [Y] by running the 

relevant rules and test the WHILE condition. As long as 

the value of [Y] was greater than 0, the program would 

continue to run rules 100-200, clearing all data before each 

run (line 14). If the variable [ABC] is less than 0 (line 16), 

the program would increment [Z] (line 17) and loop back 

to the start (line 18). 

To create a similar execution sequence in other programs 

would require several separate knowledge bases, a 

blackboard file and some technique to control the order in 

which programs were called. In EXSYS, only a single 

knowledge base is needed and the steps in the execution 

can be clearly defined. 

There are great advantages to using a Command Language 

operating over a structured set of rules for complex 

applications. The Command Language increases the 

capabilities of EXSYS software substantially and allows it 

to handle much more complex problems. 

CONFIDENCE MODES 

EXSYS Professional provides six ways to handle 

uncertain data, the confidence or probability factors within 

your expert system. The different systems are designed to 

provide a range from simple and intuitive confidence 

systems, through customized systems that enable the 

developer to implement complex ways of handling 

confidence. The confidence methods provided are: 

YES / NO System 

If the system does not require any estimate of probability, 

the YES/NO (0/1) system is best. This confidence system 

is very easy to use since the first rule that fires for a choice 

sets the value to 1 for Yes or 0 for No. No intermediate 

values are assigned. This confidence system is good for 

selecting choices from a list, an automated questionnaire, 

or other systems where the choices used by the system are 

definitely “yes” or “no”. 

0-10 System 

The 0-10 System provides confidence values on a scale of 

0-10. This is often quite compatible with the intuitive 

knowledge used in the development of an expert system. 

A value of 0 locks the value for the choice at 0 (No) and a 

value of 10 locks the value at 10 (Yes). Confidence values 

between 1 and 9 are averaged to give a relative likelihood. 

This system can positively select or reject a choice (with a 

value of 10 or 0) but can also allow intermediate values to 

indicate choices that may also be appropriate. 

When obtaining a human expert’s intuitive confidence for 

confidence in an event, a 0-10 scale is often comfortable 

and easy to use. Unless valid statistical data is available, 

precision higher than 0-10 is difficult to obtain from 

intuitive human knowledge. 

Despite its simplistic calculations, the 0-10 System is quite 

suitable for many expert systems and is easy to use. 

-100 to 100 System 

The -100 to 100 System is effective if statistical data, 

accurate to two significant figures, is available, or if the 

nature of the problem requires that the confidence factors 

be combined as dependent or independent probabilities. 

Values can be assigned to choices in the range of -100 to 

100. This provides greater resolution than the 0-10 

system. However, there is no value that locks the value at 

“yes” or “no”; values of 0, 100 and -100 are treated like 

any other value. Also, there are three methods of 

combining the confidence values - average, dependent 

probabilities or independent probabilities. 


Increment/Decrement System 

This system is intuitive and easy to use. Points are added 

to or subtracted from the total score for a choice. A rule 

can add or subtract as much as 100 points from the total 

for a choice. At the end, the total value for a choice is 

displayed. This system differentiates among possible 

solutions that would provide similar or identical scores 

using other systems. 

Custom Formula System 

This is by far the most complex of the systems. It can be 

used when a problem cannot be solved by one of the other 

systems. In this system, you can write your own formulas 

for the combination of confidence values. This provides 

enormous flexibility. One method of combining 

confidence values can be used in one part of an expert 

system and another method in the rest of the system. 

Also, in addition to the confidence associated with a 

choice, this system allows the EXSYS Professional data to 

have associated confidence values. The confidence values 

associated with the data can be asked of the user, set to 

default values, or derived from rules. The confidence of a 

choice can take into account the confidence of data 

relevant to that choice. This flexibility allows very 

complex systems of confidence factors to be implemented. 

Fuzzy Logic 

Fuzzy logic is a very powerful technique that enables you 

to build expert systems that more closely reflect the real 

world. In the Fuzzy Logic confidence mode, fuzzy 

membership functions are defined which assign 

confidence to various qualifier values based on the value 

of a variable. These confidence values are propagated 

through the rules to the confidence assigned to choices or 

other qualifiers. Specific values can be defuzzified out of 

the results to have the system give precise 

recommendations. 

EXSYS RuleBook and EXSYS RuleBook PLUS support 

the YES/NO, 0-10 and Increment / Decrement modes. 

EXSYS FRAMES 

FRAMES provide a way to handle more complex data. 

Frames allow multiple columns and complex search 

criteria with Boolean operators. The data in a frame can 

be read or updated by the expert system. Frames also 

provide inheritance which allows a hierarchical set of 

frames to be created with data in “parent” frames available 

to lower level frames. The use of frames provides a way 

for EXSYS expert systems to handle data that is portable 

across all platforms. Frame data is accessed by a FRAME 

command in EXSYS that can be used in rules, associated 

with data items, or called from the Command Language or 


EXSYS BLACKBOARDS 

Blackboards provide a flexible means for EXSYS expert 

systems, and other applications, to store and retrieve data. 


The data is typically shared between/among multiple 

expert systems and other programs in a knowledge based 

application. A set of EXSYS blackboard commands 

enable you to read or write data to the blackboard and to 

maintain the blackboard. The blackboard files are simply 

text files and can be easily read or created by other 

programs. 

PARAMETER REPLACEMENT 

Data dynamically set by the expert system can be inserted 

in any text string, formula or command. In EXSYS, 

variables are designated by including them in square 

brackets, [X]. For example, [X] would be the variable X. 

If a string contains the variable in double square brackets, 

the value/text for the variable will be inserted into the 

string before the string or command is executed. 

Similarly, qualifier text and values can also be embedded 

in a text string. 

This simple feature enables you to write dynamic 

commands that are modified and set by the system and 

user input. Notes can easily contain the actual data 

provided by the end user, or obtained from an external 

program. Complex meta-rules can be developed to step 

through arrays of data. Self-modifying command files can 

be generated. The use of parameter replacement allows 

the building of very complex systems. 

A simple example of parameter replacement is the 

development of user interfaces that reflect data input. We 

might have an EXSYS Professional variable [NAME] that is 

obtained from the user or a database which contains the name 

of the user. We could make the prompt to ask a question: 

[[NAME]], please tell me... 

EXSYS Professional will automatically replace [[NAME]] 

with the actual user name at the start of the prompt. 

This is a very simple use of parameter replacement, but it 

displays how easily such customization can be added in 

EXSYS. In other expert system shells, embedding the 

name would be difficult or impossible. 

The EXSYS RuleBook 

Developer Interface 

EXSYS RuleBook introduces a new approach to building 

expert systems rapidly. A combination of a tree structured 

representation of the knowledge and a sophisticated 

system for detecting errors in the developer’s logic has 

produced a tool that can be learned in a very short time. 

Systems developed with RuleBook can serve as stand 

alone applications or be enhanced through upward 

compatibility with the EXSYS Professional Expert System 

Development tool and EXSYS Linkable Object Modules. 

EXSYS RuleBook PLUS provides a command language 

that can be used to control the execution of the expert 

system and interface to other programs and data sources.

Expert - Checks 

the system for 

logical errors 

Choice - Define 

the goals of the 

system 

Factor - Define 

the factors 

used in the 

decision 

Tree - Define 

the trees used 

in the system 

Report - Define 

a report format 

for the 

conclusions 

RuleBook is designed to 

look like a notebook. 

Sections are divided with 

page tabs. Clicking on a 

page tab will bring you to 

the specified section. 

Expert systems can be 

developed with RuleBook 

for any problem that 

involves a selection from 

among a definable group 

of choices where the 

decision is based on 

logical steps that can be 

described as a set of tree 

diagrams. The trees can 

involve relative probabilities 

of a choice being 

correct or derive 

information used in 

other trees. 

In RuleBook, the application knowledge is represented as 

tree diagrams. RuleBook automatically converts these trees to 

IF-THEN type rules that represent the same logic and which is 

portable to EXSYS Professional. 

RuleBook is easy to use. No special languages are needed 

and a l l input is in the form of either English text, algebraic 

expression or menu selection. The developer of an expert 

system works within the EXSYS RuleBook Editor, which 

provides menus, prompts and help. It is not necessary to 

memorize complex rule syntax. 

Systems are fielded with the RuleBook Runtime program. A 

RuleBook Runtime distribution license is provided which 

permits unlimited distribution of finished applications. 

Essentially all of the instruction necessary for an end user to 

run a fielded application is provided by the program and all 

output is in English. Little or no training is required to run an 

already developed knowledge base. The end user of the 

expert system can ask HOW conclusions were 

reached or WHY information is needed. The 

program will respond with a full explanation 

of the logic used to arrive at the conclusion, 

including backward chaining. The developer 

can customize screens and decide what options 

are available to the end user. 

Building trees in RuleBook is very similar to 

drawing tree diagrams on paper. RuleBook 

provides a variety of data items to use in the 

trees and ways to edit the trees. 

TREES 

A tree is a branched decision tree that 

represents all, or a portion, of the decision 

making instructions. In RuleBook, trees 

look like the illustration to the right. 

Test 1 : Value 1 



NODES 

The tree is made up of nodes that represent decision 

branch points, and those that are assignments of value. 

These correspond to IF and THEN conditions in a rule. 

The IF nodes always have at least 2 values - and may have 

as many as 30. The various values are joined together 

vertically in a block. In the example, Test 1, Test 2 and 

Test 3 are all IF nodes. The node values can be a multiple 

choice text items, ranges of a numeric variable or 

true/false tests of a mathematical expression. 

THEN Nodes have a single value and assign a value to a 

choice (goal) of the expert system, assign text or numeric 

data, display a message to the end user, or annotate the 

tree. THEN nodes have a black triangle on their left side. 

FACTORS 

Factors are text or numeric data items that are used to 

define the nodes. There are two types of factors: 

Qualifiers and Variables. 

Qualifiers 

Qualifiers are multiple value lists. These are typically text 

and can contain up to 30 values. For example, if the day 

of the week is relevant in reaching a conclusion, we could 

have a qualifier of "Today is", with possible values: 

Monday 

Tuesday 

Wednesday 

Thursday 

Friday 

Saturday 

Sunday 

A qualifier condition is a statement in the tree (or rule) 

made up of the starting qualifier text and one or more of 

the associated values. 

Qualifiers can be used in the IF part of a tree branch to test 

a value or in the THEN part to assign a value. 





Choice 5 

Choice 1 

Choice 2 

Choice 3 

Choice 4 


Variables 

Variables contain numeric data. A variable value may be 

any value between its upper and lower bounds. For the 

purposes of building the tree, the value of the variable is 

divided into numeric ranges defined by the logical break 

points in the decision making process. 

CHOICES 

Choices are the goals that the expert system will decide 

among. A system to identify types of flowers would have 

the various species of flower as choices. A system to 

determine the cause for a failure in a machine would have 

the possible items that could break as choices. Depending 

on the Confidence Mode used, a choice may be assigned a 

confidence value to determine its relative likelihood. 

Choices can be used in the THEN part of branches only. 

Take a very small example identifying items on the desk: 

YES 

Makes 

noise? 

NO 

Color? 

Black 

White 

Black 

Flat 

T E L E P H O N E 

C O M P U T E R 

FLOPPY DISK 

P A P E R 

P E N C I L 

C y l i n d r i c a l 

When converted to RuleBook form this will look like: 

Makes Noise: YES 

Makes Noise: NO 

Color? 

Shape 

White 

Color: Black 

Color: White 

Color: Black 

Color: White 

It is easy to draw a tree on paper. It is just as easy to draw 

a tree in RuleBook once the editing commands are 

learned. 

BALLOONS 

RuleBook automatically converts each branch of the tree 

to an IF-THEN rule. To see the rule that is associated 


Telephone 

Computer 

Floppy Disk 

Shape: Flat 

Shape: Cylindrical 

with any branch, click on a node. A balloon will be 

displayed showing the rule up to that node. For example, 

a click on the box labeled Computer would display: 

Color: Black 

Color: 

Color: Black 

Color: 

ADDING NODES TO A TREE 

When a new tree is created, it will only have a terminal 

node that says "Double Click to Add Factor". 

Paper 

Pencil 

Telephone 

Computer 

Floppy Disk 

Shape: Flat 

Shape: Cylindrical 

Tree Name 

Double Click to Add Factor 

IF 

Makes Noise: YES 

and Color: Black 

THEN 

Computer 

Paper 

Pencil 

▲ 

▼ 

To add a factor to the tree, double click 

on the terminal node. This will bring up 

a dialog box for adding factors.

Qualifier 

Select qualifier by text or name: Find Find Again 

The color of the flower is 

The stem is 

The size of the flower is 

The leaves are 

Red 

White 

Yellow 

Orange 

Blue 

Green 

Other Values: 

Individual 

New Qual. 

OK Group All Together 

Custom 

Cancel 

A qualifier condition for the color of a flower, could be 

added by clicking on the TEXT button in the Add IF 

Factor box. This would display a dialog box with all of 

the qualifiers. 

In this case the statement that "The color of the flower is 

Red" has been selected. This will be added to the tree. 

The color of the flower is red 

The color of the flower is white 

The color of the flower is yellow 

The color of the flower is orange 

The color of the flower is blue 

The color of the flower is green 

Control for grouping 

other values 







The node that was added takes into account all possible 

answers that the end user may provide for the qualifier. 

The value we selected, "The color of the flower is red", is 

in the top line, but branches were automatically created for 

the other possible answers. The result is six branches each 

with a terminal node. In this way, RuleBook automatically 

creates branches and guarantees that the tree will be 

c o m p l e t e . 

Having RuleBook generate branches also 

helps to extract information from the 

system developer. It forces the developer 

to consider all possible cases. When the 

RuleBook Expert function checks the 

trees, it will report any branches that have 

not been completed. 

In some cases, it is not desirable to add a 

separate branch for each of the other 

possible values of the qualifier. 

RuleBook provides three options. At the 

bottom of the dialog where the qualifier 

and value was selected is a set of radio 

buttons that control how the other values 

are grouped: 

In the example, the default of 

"Individual" was selected. This causes 

each of the other values to be given an 

individual branch. 

The second option is "Group ALL 

Together". This causes all of the other 

values to be put in a single branch. If this 

had been selected, the tree would look 

like: 



OR yellow OR orange OR 

blue OR green 



There would only be two branches from the node. 

The third option is to do custom grouping of the other 

values. This provides custom control for the number of 

branches created and what values are associated with 

them. Selecting the "Custom" option displays the dialog: 

Group Values in Group: 

1 

2 

New 

Delete 

OK 

Cancel 

Add to Group Add All Delete from Group 

Values in Group: 


This dialog would allow selection of the following custom 

groups: 

Group Values 

1 Red 

2 Yellow, Orange 

3 Blue, Green 

4 White 

This would build the node: 


The color of the flower is 

yellow OR orange 

The color of the flower is yellow 

OR blue OR green 






In this case four branches were created. The Custom 

option gives total control on the number of branches and 

values associated with them. 

The ability to add nodes rapidly with a point and click 

interface, plus RuleBook's feature of expanding the tree to 

consider all possible combinations of input, allows rules to 

be built very rapidly. The developer is prompted to 

consider all possible cases, which can be an excellent way 

to extract knowledge from the developer and guarantees 

system completeness. 

In most applications there would be multiple trees each 

representing a different aspect of the decision making 

problem. Trees can assign values in their THEN part. If 

other tree nodes require these values, the appropriate rules 

will automatically be called through backward chaining. 

The trees can be printed and discussed with other 

experts. Since the trees are easy to read, this 

facilitates group consensus on the application, even 

by experts not using RuleBook. 

THE RULEBOOK EXPERT 

RuleBook has a built in Expert to automatically 

validate the system and check for a variety of errors 

that may have been made in the trees. The expert is 

run by clicking on the Expert tab to display the 

Expert window. 

To have the Expert check the system, click on the 

Check System button. If there is a red border around 

the button, the trees have been changed since the last 


check and it is time to recheck the system. If there is 

no red border the trees have not been changed since the 

last check. 

The Expert does two different checks of the system. The 

first looks for errors that can be found rapidly. The second 

part actually runs the rules with all of the possible 

combinations of input data. Sets of input are 

systematically generated, and used to test the rules. During 

the test, the Expert looks for various types of errors. 

Systems developed with RuleBook can be automatically 

checked by the Validation Expert before fielding the 

application. The validation testing runs automatically and 

for larger systems can be done over a weekend or 

vacation. 

When the Expert checks the system, it will report on a 

variety of errors: 

Incomplete Branches 

Text Factors Not Used 

Variables Not Used 

Choices Not Used 

Text Factors Not Always Derived 

Variables Not Always Derived 

Multiple Factors Use 

Input Produces No Output 

Variable Assigned a Value out of Range 

Too Many Values for Text Factor 

Loop Error 

RULEBOOK - THE BOTTOM LINE 

The combination of the easy tree diagram developer 

interface plus the ability of RuleBook to check an 

application for many common errors makes it the ideal 

tool for rapid system development. RuleBook is an 

excellent choice for diagnostic problems, help desks 

and other areas where the logic can be described as a 

tree diagram. 

Expert 

Problems: 

Help! 

Check System 

Details Report

EXSYS RuleBook PLUS 

RuleBook PLUS uses the same tree structured developer 

interface as EXSYS RuleBook. It adds the EXSYS 

Procedural Command Language and interfaces described 

later. These additions allow complex procedural operations 

to be separated from the logic of the rules. The procedural 

operations are defined in an easy to read procedural 

language. The ability to run subsets of the rules through 

the procedural operations allows modularizations and more 

complex systems to be built. 

RuleBook PLUS adds interfaces into many SQL 

databases and spreadsheets to automatically obtain 

data needed by the application. It supports the 

EXSYS Professional frame-based knowledge 

representation, black boards to share data between 

applications and interfaces to the LINDO linear 

programming tool for optimization systems. 

RuleBook PLUS allows any program that can be 

run on your computer to be called from an 

application with data passed to and from the 

called program. 

RuleBook PLUS is especially effective at process 

control applications and for expert system 

development where the basic logic can be 

described as a set of tree diagrams, but where 

external interfaces or procedural control is 

required. 

EXSYS Professional Developer 

Interface 

RuleBook is an ideal way to rapidly develop systems that 

can be described as a set of tree diagrams. However, the 

logic of some systems can not be described as trees. 

These systems require that individual rules be built. 

EXSYS Professional provides a rule editor for this task. 

Since RuleBook systems are upwardly compatible with 

EXSYS Professional, developers will often do as much as 

possible with a tree representation and then move to 

EXSYS Professional to add the non-tree structured logic. 

As an expert system developer using EXSYS Professional, 

you have a wide range of tools available for rule entry, 

editing, debugging, tracing and validation. 

EXSYS PROFESSIONAL RULE EDITOR 

The EXSYS Rule Editor is a powerful and flexible tool for 

expert system development. Using it, you can rapidly set 

the various parameters for the expert system and enter/edit 

rules. When you want to test the rules, select "RUN" from 

a menu and you are running. If you want to cancel a run 

and return to edit mode, just make another menu selection 

and you are back in the edit mode. 

This rapid edit-test-edit cycle speeds expert system 

development. It is made possible by EXSYS 

Professional's incremental compiling of the rules as they 

are entered. As each rule is input, it is compiled to 

EXSYS's internal representation. This means that the rule 

editor has access to the logic of the rules already entered. 

If you enter a rule that is potentially in conflict with an 

existing rule, the editor will immediately tell you and give 

you the opportunity to correct it. 

Rule 24 

and The color of pipe A output is brown 

Rules are entered in a window that looks like: 

Clicking on the qualifier button brings up a list of the 

qualifiers in the system and their associated value lists. To 

build a qualifier, simply click on the desired qualifier and 

the desired value(s). The condition will appear in the rule 

window. You only have to type the qualifier text when it 

is first created or if it needs to be edited. Mathematical 

expressions and choice conditions are just as easy to input. 

If you want to add a custom command or access data from 

another program, click on the Command button. Just fill 

in data in a few of the dialog boxes and EXSYS will build 

syntactically correct commands for you. You do not have 

to memorize the command syntax. 

Frequently the first few conditions in a rule will be identical 

to the previous rule. Just click the Repeat button once for 

each condition and they will be copied into this rule. 

Rule editing is just as easy. Simply select a rule to edit and 

change, delete or add conditions. Conditions may also be 

cut or copied from other rules. 

CONFIGURATION OPTIONS 

You have control over many of the ways in which EXSYS 

Professional operates through configuration option 

commands. This enables you to fine tune the performance 


of the shell for a specific application, or for all of your 

development. Configuration options are listed in files that 

are automatically read when EXSYS Professional starts. 

One file is global for all applications developed and 

another is specific to the individual application. 

Configuration options have been developed for the many 

cases where some users need EXSYS Professional to work 

one way and others need something different. For 

example, EXSYS has default colors - if you would prefer 

other colors, you can set them with configuration 

commands. If you do all of your development on a 

computer with a color monitor, but want to see what an 

application will look like delivered on a monochrome 

laptop, you use just one configuration command. Likewise, 

EXSYS Professional has certain messages it displays that 

can be redefined with configuration commands. 

Configuration options also control the actual functioning of 

the inference engine. The choice between forward and 

backward chaining can be made with a configuration 

option. With a single command line in the configuration 

file you can run in a batch mode, have the display of final 

choices be unsorted, disable screen output, fine-tune 

chaining on variables or perform many other operations. 

Configuration options also allow you to tune the end user 

interface. You may not want the end user to be able to 

perform some operations such as displaying rules. These 

can be disabled with configuration options. 

With over 140 commands, there are many ways to tune 

EXSYS to your needs. 

FUZZY LOGIC 

EXSYS Professional supports fuzzy logic. Fuzzy logic is a 

way to build systems that much more closely reflect the real 

world. Fuzzy logic is often presented as a very complex 

technique, but it does not have to be. EXSYS Inc. has a 

long history of taking complex knowledge representation 

concepts and making them easy to use. This same 

philosophy has been applied to fuzzy logic. The powerful 

and useful part of fuzzy logic is available, but the complex 

mathematics is hidden from the developer. 

The temperature is 


To see how EXSYS implements fuzzy logic, lets look at 

an example: 

Suppose you are building an expert system to control the 

temperature of hot water fed to a machine. In a non-fuzzy 

system, you might have a rule 

IF 

THEN 

The input water is too hot 

Mix cold water with the 

input stream 

When this rule is run, it will ask the end user if the input 

water is "too hot". Since this is a somewhat ambiguous 

question, you could add a rule to derive more specific 

information. 

IF 

THEN 

[INPUT TEMP] > 180 


Now the system will ask about the water temperature. 

This information might come from the end user or directly 

from instrumentation. 

The problem with this approach, is nothing happens at a 

temperature of 179.9999 and the system may add too 

much cold water at 180.0001. This can result in the 

temperature being put into oscillation rather than being 

brought to the desired temperature smoothly. 

The situation would be improved by adding more rules 

IF 

THEN 

IF 

THEN 

IF 

THEN 

The input water is a 

little too hot 

The amount of cold water to 

add to the input is 

a little 



add to the input is medium 

The input water is way too 

hot 


add to the input is a lot 

with temperature rules to derive the values 

IF 

THEN 

[INPUT TEMP]

IF 

[INPUT TEMP] > 160 

and [INPUT TEMP] < 180 

THEN 

The input water is a little 

too hot 

IF 

[INPUT TEMP] >= 180 

and [INPUT TEMP] < 200 

THEN 


IF 

THEN 

[INPUT TEMP] >= 200 

The input water is way 

too hot 

This breaks up the single step function into three steps. As 

the input water gets a little too hot, you try adding a little 

cold water. If this is not enough, and the temperature of 

the input water continues to rise, at 180 you increase the 

amount of cold water added. If the temperature reaches 

200, you increase the amount of cold water again. 

The three step system clearly is better at controlling the 

process and more closely reflects the way a human 

operator would react. A hard break point at 180 in the first 

system has been made slightly "fuzzier" by breaking it into 

three steps. But you had to write three times as many 

rules to do it. Suppose you want to break the process into 

100 steps and have many functions to control. The 

number of rules needed would become enormous and 

impractical. What would be best, is to make it a 

continuous function rather than a series of steps. The 

solution is Fuzzy Logic. 

How Fuzzy Logic Is Implemented in 

EXSYS Professional 

Fuzzy logic is a technique of assigning degrees of 

confidence to various possible options, based on the value 

of a variable. In the rules we did this in a crude way that 

could be diagrammed in a graph as: 

C 

o 

n 

f 

1 

0 

OK little too hot too hot way too hot 

150 160 170 180 190 200 

T e m p e r a t u r e 

The confidence for each of the three possible values is 

either 0 or 1 depending on the temperature. There is no 

overlap and the confidence changes abruptly at a specific 

break point. 

It would be better to gradually increase the confidence in 

each of the values as the temperature increases. 

As a graph, this would look more like: 

C 

o 

n 

f 

1 

0 

way too 

OK little too hot too hot hot 

150 160 170 180 190 200 


In this system, as the temperature increases, the 

confidence in each of the three ranges will gradually 

increase (and in some cases, fall off) smoothly. At a 

temperature of 152, the confidence in "a little too hot" 

starts to increase from 0 and reaches 1 at 162. The 

temperatures between 152 and 162 give a continuous 

smoothly increasing confidence value. For any 

temperature, the graph shows the confidence in each of the 

values. Notice that for some temperatures, you have some 

confidence in two different values. At 175, "a little too 

hot" has a confidence of .8 and "too hot" has a confidence 

of .4. This is a great advantage, since you want the rules 

based on "too hot" to kick in gradually, rather than 

suddenly at a threshold value. 

In a fuzzy system, there is a confidence associated with 

EACH VALUE of a qualifier - not just the qualifier as a 

whole. 

These graphs of confidence in a qualifier value, versus a 

variable (temperature) are called "membership functions" 

and are the key to making an expert system "fuzzy". For 

a simple case like this, it would be possible to write a 

series of rules that calculated the confidence, but it would 

be very cumbersome, even for this simple problem. 

In EXSYS Professional, fuzzy logic is implemented by 

two simple techniques: 

1. QUALIFIERS can be made fuzzy based on 

an EXSYS variable and membership functions. 

Membership functions are defined with a point 

and click graphical user interface that provides 

easy visualization. 

2. VARIABLES can be "de-fuzzified" based on 

the weighted average of a qualifier's confidence 

values. This is how a fuzzy system ends up 

giving a precise recommendation. (More on this 

later.) 

Use of the existing EXSYS Professional data elements 

(qualifiers and variables) makes the addition of fuzzy logic 

to applications very easy. 


Returning to the example, in a fuzzy logic version you 

would have 4 simple rules. 

IF 

THEN 

IF 

THEN 

IF 

THEN 

IF 

THEN 

The input water is OK 


add to the input is none 

The input water is a little 

too hot 


add to the input is a 

little 



add to the input is medium 

The input water is way 

too hot 


add to the input is a lot 

Now you do not have to create a set of rules to convert a 

temperature to a qualifier value. Instead you simply click 

on the "Fuzzify" box when defining the qualifier. 

A screen is displayed that allows you to define the 

membership function. 

Qualifier 

Value: 

1 

.8 

.6 

.4 

.2 

0 

OK 

Value: ▼ 

1 100 

Cancel 

Zoom In 

Zoom Out 

U p d a t e 

Zoom In 

Variable: 

TEMP 


H Pos Conf 

Do NOT Fuzzify 

The membership function is defined by clicking on the 

graph to indicate the shape of the function, or point 

coordinates are directly entered into a table. Each value of 

the qualifier has a separate membership function, and each 

function is made up of as many as to 8 straight line 

segments. Therefore, complex membership function sets 

can be defined. A test function enables you to easily 

check the confidence of each qualifier value for any value 

of the variable. The graph window can be scrolled and 

rescaled to display the entire set of membership functions. 

For this problem, the membership functions are drawn to 

look like: 

1 

C 

o 

n 

f 

0 

way too 

OK little too hot too hot hot 

150 160 170 180 190 200 


Once the membership function is defined for the qualifier, 

you do not need to add additional rules to derive the value 

for the qualifier. When the qualifier value is needed, 

EXSYS Professional will automatically ask the value of 

the associated variable "temperature". The confidence of 

the appropriate qualifier values will then be set, based on 

the temperature. This confidence is automatically passed 

through to the items set in the THEN part. 

For example, at a temperature of 175, "a little too hot" has 

a confidence of .8 and "too hot" has a confidence of .4. 

Based on the rules, "add a LITTLE water" 

would get a confidence of .8 and "add 

MEDIUM water" would get a confidence of 

.4. If the rules had more than one IF 

condition, the confidence of the IF parts 

would be combined before assigning the 

New 

confidence to the THEN part. The way the 

IF confidence is combined is handled 

automatically by EXSYS. In an actual 

▼ system, many factors would be taken into 

account to determine the confidence values 

of the "amount of water to add". 

D e f u z z i f i c a t i o n 

Now you have a system that gives levels of 

confidence in the various amounts of water 

to add. The problem has been made fuzzy, 

and the answer we get is certainly fuzzy. 

In a plant environment, we do not want to 

tell the operator that "a little water should 

be added with .8 confidence and a medium 

amount of water should be added with .4 

confidence". The operator just wants to 

know how much water to add. This is "defuzzification" 

- taking a fuzzy statement and 

converting it back to a precise number.

In EXSYS Professional, to make a qualifier fuzzy, you 

associate a variable. To de-fuzzify a value for a variable 

you associate a qualifier. This is typically a weighted 

average of the various confidences assigned to the 

qualifier values. For example, suppose you have a 

variable [WATER TO ADD] and you base its value on the 

de-fuzzification of the "add water" qualifier. You could 

use the formula: 

[WATER TO ADD] = 2 * (confidence in "add a LITTLE") + 

5 * (confidence in "add MEDIUM") + 

10 * (confidence in "add ALOT") 

In this example, it would be (2*.8) + (5*.4) = 3.6 

This is about what you would expect. It is more than "add 

a LITTLE" amount of 2 but less than the "add MEDIUM" 

amount of 5. 

Advantage of Fuzzy Sets 

The first one rule non-fuzzy system would have an "add 

water" graph that would look like: 

W 

a 

t 

e 

r 

Clearly a very crude control. 

With three rules, but without Fuzzy Logic, the graph 

improves to: 

W 

a 

t 

e 

r 

But when you add Fuzzy Logic, you easily obtain a 

continuous graph: 

W 

a 

t 

e 

r 

150 160 170 180 190 200 


150 160 170 180 190 200 


150 160 170 180 190 200 


This is a much better way to control the process since it 

will tend to make corrections smoothly. The exact shape 

of the graph is determined by the shape of the membership 

functions. 

EXSYS Professional automatically handles the 

mathematics for assigning and propagating the Fuzzy 

Logic confidence values. Configuration options allow 

some control over the formulas used. For detailed control, 

EXSYS Linkable Object Modules allows access to the C 

source code used for the formulas used to combine Fuzzy 

confidence. For special applications, these formulas can 

be customized by the developer. 

Fuzzy Logic can also be used to assign confidence to 

qualifiers. It is particularly effective in systems for 

process control 

DEBUGGING 

Whenever you are writing down the logic of a process, 

either in programming or in building an expert system, 

errors will occur. Tracking down the errors can take time 

and effort. EXSYS Professional provides a variety of 

tools to assist you in debugging your systems. A trace 

window displays the history of the session – the order in 

which the rules fired, what data was set, etc. This allows 

you to follow exactly what happened and find the error. 

This trace can also be directed to a file for later reference. 

During a run, whenever EXSYS Professional asks for 

data, you can ask "WHY" it is asking. EXSYS will 

display the logic that required that item of data. Also you 

can display any rule, the data known to the system and the 

status of the choices. In all cases, you can ask how a 

particular item of data was derived to trace back the logic 

and find any errors. 

EXSYS can also generate cross reference listings to show 

you where data items are used and what rules assign 

values to variables, etc. 

EXSYS PR O F E S S I O N A L AU TO M AT I C SY S T E M 

VALIDATION AND TREE DIAGRAMS 

Testing and validating an expert system must be a major 

part of any expert system development project. It is 

important to make sure end users will get valid answers to 

any input. EXSYS Professional's automatic validation 

function greatly simplifies and automates this process. 

EXSYS will automatically test your application, 

unattended, for a variety of errors. Your applications may 

be tested overnight or while you are on vacation. 

EXSYS Professional supports two methods of validation 

testing; systematic and random. Systematic testing allows 

all possible combinations of input to be tested for a variety 

of possible errors. If the expert system is very large and 

systematic testing of the entire system would take too 

long, testing of portions of the system or random testing of 

the entire system can be performed. 


Three files are produced - two types of tree diagrams, and 

an error report file. The tree diagram shows all of the 

possible combinations of input and the resulting output of 

the system. Regardless of the complexity of the logic of 

the system, the input and output can always be 

diagrammed as a tree. The trees can be examined with a 

special display routine in EXSYS that enables you to 

scroll through the tree diagram. The nodes on the diagram 

are written in an abbreviated form, e.g. "Q3:2", means 

qualifier number 3 value 2. When the tree diagram is 

displayed, a mouse click on the node expands the 

abbreviated form to the full text form of the qualifier or 

variable. 

The two types of tree diagrams produced are linear and 

branched tree diagrams. They are equivalent in 

information content, but are diagrammed differently. The 

branched tree diagram graphically shows the branching in 

the system. 

For example: 

Q7:1 [X]:30 Q4:1 >>> C3:7 C2:1 

Q4:2 >>> C3:5 

Q4:3 >>> C1:2 C4:8 

[X]:35 Q4:1 >>> ERROR: Q6 could not be derived 

Q4:2 >>> C5:7 

Q4:3 >>> C6:6 

[X]:40 Q9:2 Q11:1 >>>C4:6 

Q11:3 >>>C5:2 

Q11:4 >>>C5:7 

Q7:2 Q11:1 >>>ERROR: No Choices set 

Q11:2 >>>ERROR: Q4 loop error 

Q11:3 >>> C6:3 C5:1 

Q11:4 >>> C3:4 

This is convenient for seeing the overall structure, but if a 

particular set of input produces an error, in a large tree it 

may take some scrolling to read all of the information on 

the input. 

In a linear tree diagram, all of the node values for a branch 

are displayed on a single line. The same tree would be 

displayed as: 

Q7:1 - [X]:30 - Q4:1 >>>C3:7 C2:1 

Q7:1 - [X]:30 - Q4:2 >>>C3:5 

Q7:1 - [X]:30 - Q4:3 >>>C1:2 C4:8 

Q7:1 - [X]:35 - Q4:1 >>>ERROR:Q6 could not be derived 

Q7:1 - [X]:35 - Q4:2 >>>C5:7 

Q7:1 - [X]:35 - Q4:3 >>>C6:6 

Q7:1 - [X]:40 - Q11:1 >>>C4:6 

Q7:1 - [X]:40 - Q11:2 >>>ERROR: Variable out of ... 

Q7:1 - [X]:40 - Q11:3 >>>C5:2 

Q7:1 - [X]:40 - Q11:4 >>>C5:7 

In the linear tree, it is easier to follow the data that lead to 

the conclusion, since all of the data is on a single line. 

When random testing is selected, only a linear diagram 

will be created. Due to the random nature of the testing, 

the data will not be tree structured. 


The error file contains reports of any detected errors which 

were detected and the input which produced the error. 

The validation function will detect and report 

combinations of input that: 

• Produced no conclusions. 

• Failed to derive needed qualifiers or variables 

that should be derived. 

• Created loop errors. 

• Assigned a variable a value which is outside of 

the limits specified. 

• Assigned more values to a qualifier than the 

maximum number allowed. 

• Failed special custom tests designed with the 


EXSYS Professional also provides statistics on rule 

utilization, especially rules not used, and statistics on the 

assignment of confidence factors for conclusions. You 

can examine these statistics to see if they are what you 

would expect. 

In most expert systems, some questions will only be asked 

when the user answers preceding questions in a particular 

way. In EXSYS's validation mode, only the combinations 

of input that might actually be supplied by an end user are 

considered. This usually reduces the number of tests that 

must be run to far less than the total number of all possible 

combinations of data. 

You can either test the entire system, or limit the testing to 

part of the system by reducing the number of parameters 

that EXSYS tests. Once the parameters are set, EXSYS 

Professional takes over and runs unattended. 

Most validation tests run quickly. Depending on the size 

of the application and speed of the computer, tens of 

thousands to hundreds of thousands of tests can be run 

overnight or over a weekend. Just start the EXSYS 

Professional validation and you will have a report of any 

errors it finds when you return. 

Validation testing is also a very valuable system 

maintenance tool. If you make some changes in your 

computing environment and want to make sure your 

applications are still performing correctly, create a 

validation test file, change the environment and create a 

new validation test file. The two files should be identical. 

If they are not, you can compare them to see where 

problems have developed. 

VALIDATION GRAPHS 

EXSYS Professional provides a way to graphically 

examine the data produced during system validation. This 

is a very powerful way to examine the effects changing a 

variable may have on the results in a multi-variable system. 

Both the values of variables and choices can be examined.

For example, suppose a system uses a variable 

TEMPERATURE (plus other data) to determine the 

confidence in a choice "ADD WATER". We could select 

TEMPERATURE as the graph variable. If we did not add 

any other constraints we might get a graph: 

90 100 110 120 130 

TEMPERATURE 

This graph has a band of values that indicate the possible 

range of values of the choice ADD WATER for each 

temperature tested in the validation test. Remember that in 

the system there are other factors besides temperature that 

determine the final results. For example, at a temperature 

of 120, all possible combinations of input which produced 

a confidence for ADD WATER were taken from the 

validation test tree. The maximum and minimum values 

are displayed and combined for each temperature to make 

the graph. The values graphed can come from fuzzy logic 

systems, and are an excellent way to visualize the effects 

that changing membership functions have on the overall 

control strategy. 

By limiting various input parameters, the graph can be a 

very effective way to examine the results of a system for 

many different sets of input data. 

EXSYS PROFESSIONAL RULE COMPILER 

The EXSYS Rule Compiler allows a text representation of 

expert system rules to be compiled to the internal EXSYS 

knowledge base representation. The files produced by the 

Rule Compiler can be run with the EXSYS Professional 

Runtime or Rule Editor. There are many very substantial 

advantages to using the EXSYS Rule Editor over a text 

editor for most expert system development, however there 

are certain cases where the text editor approach has 

advantages. The Rule Compiler is designed to be used 

when these cases arise. 

Due to the nature of a compiler, certain syntactical 

information must be provided in the rules. The program 

has to be able to tell a qualifier from a formula, from a 

choice, etc. This is a problem found in all rule compilers. 

(The EXSYS Rule Editor "knows" the difference from the 

button pressed and the items selected.) In EXSYS 

Professional, the extra syntactical notation has been kept 

to a minimum and the text editor representation of the 

rules looks as much like the standard text representation as 

possible. The required syntax information does not make 

the rules difficult to read. 

The EXSYS Professional Rule Editor has an option to 

print the rules with the extra syntactical information 

needed for the Rule Compiler, included. Such a file can 

be directly converted back using the Rule Compiler. This 

option of the Rule Editor plus the Rule Compiler allows 

easy incorporation of text editing in the development 

cycle. 

EXSYS REPORT GENERATOR 

EXSYS RuleBook, RuleBook PLUS and Professional 

have a Report Generator language that allows you to 

specify exactly what information is to be output and in 

what format. The Report Generator language is easy to 

learn with very simple commands. For example, the 

command "V" outputs all variables with their values. The 

command "C" outputs all choices. However, each 

command has many optional parameters that can be added 

to the basic command. For example C3 >6 /"XXXXX" 

will print the string XXXXX if choice 3 has a value 

greater than 6. There are many options for positioning 

text. For complex forms, there is a program where you 

define a form with blanks and EXSYS will fill in the 

blanks with the desired information. 

The report generator output can go to a file or printer. A 

single command will display the text file created by the 

report generator and allow the end user to scroll through it. 

The report generator can even be used to generate EXSYS 

Professional Custom Screen command files that are then 

displayed to the end user with active GUI controls such as 

buttons, graphical images or even multimedia. 

EXSYS End User Interface 

EXSYS RuleBook, RuleBook PLUS and Professional give 

you the tools to design and control the end user interface. 

Custom screens control the way questions are asked. The 

Configuration options and the Report Generator give you 

complete control of how the results are presented to the 

end user. Custom help and Hypertext enable you to 

provide multilevel, context sensitive help to your users. 

All EXSYS development tools allow immediate running 

and testing of the rules in a system by selecting "Run" from 

the menu. A run can be cancelled at any point and returned 

to the edit mode. A separate Runtime program allows 

dissemination of the finished application to end users. 

EXSYS PROFESSIONAL CUSTOM SCREENS 

End user acceptance is the key to successfully fielding 

expert systems. EXSYS has a standard way to ask 

questions, but you may want to change the look and feel of 

the EXSYS questions. This is easily done with the 

Custom Screen language. EXSYS RuleBook, RuleBook 

PLUS and Professional support custom screens. A text 

file is created with commands that define the screens you 

want to use. Commands are typically one line and enable 

you to draw boxes, set colors, draw lines and add GUI 

controls such as buttons, check boxes, radio buttons, scroll 

bars, text edit regions, meters, etc. 


Once a screen is defined with custom screen commands, it 

is portable across the various platforms. The same custom 

screens work on MS-Windows, Macintosh, VMS/Motif, 

Sun Open Look and OS/2 Presentation Manager. 

Most custom screens are associated with specific EXSYS 

qualifiers or variables. When EXSYS needs to ask the end 

user for data on a qualifier or variable, it automatically 

uses the associated custom screen. Custom screens can 

return data for a single item or for many. 

Customs screens in MS-Windows can use .PCX graphics 

files as backgrounds or as part of the screen. For 

monitoring applications and displaying the status of 

process parameters, a METER command creates and adds 

a dynamic, automatically animated graphical display. 

Example: 

This is a screen with simple YES / NO buttons and some 

buttons for asking for additional information. It also has 

some buttons that allow the end user to ask for system 

information such as KNOW, WHY and HELP. 

The WARNING light is ON: 

YES NO 

WHY KNOWN EXIT HELP 

Examples of other custom screens are: 


Reconnecting CABLE A to the system with the power 

on and a signal in the amplifier produces: 

No signal 

S t a t i c 

Intermittent Static 

C l i c k s 

Loud POP 

Good Sound 

Connecting the cable to the system 

should be done with care. First turn 

off all power to the system. Check 

that all lights are off. Make all 

connections and then turn power 

back on, starting with the preamp. 

Turn the amplifier on last. If the 

system make a loud noise, turn it 

off immediately and check the 

fuses. 

Select the filter pattern to apply to the signal: 

20- 40- 80- 160- 320- 640- 1k- 2k- 4k- 8k- 

40 80 160 320 640 1k 2k 4k 8k 16k 

▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ 

50.5 50.5 50.5 50.5 50.5 50.5 50.5 50.5 50.5 50.5 

Name and Address 

Phone 

Social Security # 

OK 

Male 

Female 

OK 

Experience 

Technical 

Sales 

Management 

Clerical 

Other 

Highest Education Degree 

HS MS 

BS PhD 

Comments 

EXSYS EXDE S I G N CU S TO M SC R E E N DE S I G N 

PROGRAM 

The EXSYS ExDesign Screen Layout program allows 

EXSYS screens to be easily designed in a "paint" style 

program. Buttons, scroll bars, lines, arrows, list boxes, mouse 

regions, graphics, etc can be added to a screen, resized and 

moved with the mouse. EXSYS custom screen files are text 

files and can be edited with any text editor. ExDesign 

automatically generates these files for any screen desired. 

ExDesign can also be used to design screen templates that 

apply to all screens in a system.

SCREEN TEMPLATES 

Custom screen templates are generic custom screen 

designs that automatically apply to all of your qualifiers or 

variables. The entire look and feel of the end user 

interface can be modified by creating a single screen 

definition. The template screen is designed with 

replaceable parameters for the qualifier, qualifier values 

and variable prompt text. Whenever a qualifier is needed, 

the text specific to that qualifier will be used to replace the 

parameters. Qualifier value text can be automatically 

used to label buttons, define mouse "hot spots" or be 

included in list boxes. Variables can use the prompt text 

and an edit region to ask for the value. A single template 

applies to all of the qualifiers or variables in the system. 

CUSTOM HELP 

EXSYS supports context sensitive help with a file of 

custom screens associated with specific qualifiers and 

variables. This is very similar to the file of custom screens 

that EXSYS will use to ask questions, but these screens 

are designed to assist users in what a question means. The 

screens are designed with the EXSYS Professional screen 

design tool. If a user is asked a question, and they need 

clarification, they can select "More Information" off the 

menu and the Custom Help screen will automatically be 

displayed. These help screens are optional and if your 

application does not need them, they can be omitted. 

HYPERTEXT 

EXSYS RuleBook, RuleBook PLUS and Professional 

have a built in Hypertext system that can be added to your 

applications. Hypertext is a another way of adding 

multilevel help for your end users. Like the Custom Help 

screens, Hypertext screens are designed with the EXSYS 

Professional screen design tool. However, instead of 

being associated with a specific EXSYS variable or 

qualifier, they are associated with a hypertext keyword. 

These hypertext key words are marked in your application 

by putting "^^" before and after the keyword. EXSYS 

will not display the ^^ but will instead automatically mark 

the keyword in reverse video anywhere it appears in your 

application. If the end user double clicks on the keyword, 

EXSYS will automatically bring up the associated 

hypertext screen. That screen may contain other hypertext 

keywords that will bring up other screens, etc. On some 

platforms, hypertext screens support multimedia interfaces 

such as laser disk video, which can be added to your 

applications. 

For example, to add hypertext to the EXSYS qualifier 

"The color is red", we could simply change the text to 

"The ^^color^^ is red". Now anywhere the qualifier is 

used, the word "color" will automatically be highlighted as 

a hypertext keyword. A double click on "color" will bring 

up the screen that is associated with the word "color". 

WHY AND HOW 

While the end user is running the system, they can ask 

questions, just as if they were working with a human 

expert. They can ask why a question is being asked. 

EXSYS will display the rules it is currently testing, that 

require the information. Because EXSYS rules use 

English statements and algebraic expressions, without 

complex syntax, it is easy for even novice users to read 

and understand the rules. At any time during the run, the 

end user can display the facts known to the system and ask 

how a fact was derived. EXSYS will explain the source of 

the data. 

When the conclusions of the system are displayed, the user 

can ask how a conclusion was reached and EXSYS will 

display the rules used. 

CHANGE AND RERUN 

At the end of a session, when the results are displayed, the 

end user may chose to display all of the data they input. 

They can then change one or a few of the answers and 

rerun the expert system with the new data. EXSYS will 

display the old and new results side-by-side for 

comparison. This type of "WHAT-IF" testing is very 

useful when the end user was not sure of a particular 

answer. By comparing the affect of an answer on the 

results, they can determine whether a particular question is 

critical to conclusions. They can examine the sensitivity 

of the conclusions to that answer. This change and rerun 

can be repeated as often as needed. 

TEXT EXPLANATION 

In many expert systems, it is desirable to give the end user 

a text explanation of what the system did. This is easily 

implemented in EXSYS. Each rule can have an associated 

Note or Reference. Notes can be used to explain the 

meaning of the rule, and references can be used to give the 

source of the fact represented by the rule. The notes in all 

of the rules that fired during a session can be put into a 

report with a single command. The notes may have the 

actual values for variables or qualifiers included with 

parameter replacement. The report file produced will be 

an English text explanation of what the system did, and 

can be displayed to the end user or saved with the system 

recommendations. 

UNDO 

If the end user makes a mistake answering a questions, 

they can select "Undo" and backup and correct errors up to 

ten questions back. 

REPORT GENERATOR 

EXSYS has a flexible report generator to output the results 

of a run to files or other programs. 

HISTORY 

In some applications it is desirable to keep a history of 

user input and interaction with the system. This can easily 

be done. 

INTEGRATION 

EXSYS Professional has a very open architecture. It can 

be integrated with your existing applications. EXSYS can 

be front ended by programs to provide data. EXSYS can 


provide the results of a run to other programs and EXSYS 

can call other programs during a run for data acquisition or 

other functions. 

DDE LINKS 

Using the EXSYS Linkable Object Modules, the EXSYS 

inference engine can set up DDE links with other 

applications running under MS Windows or Windows NT. 

EMBEDDABILITY 

Using the EXSYS Linkable Object Modules, the EXSYS 

inference engine can be invisibly embedded within another 

applications. This allows total control over the user interface. 

EXSYS Professional Linkable 

Object Modules 

EXSYS Professional is designed to be a general use expert 

system shell. It allows a wide range of functions to be 

performed. However, sometimes a special application 

requires a high degree of customization and modification 

of the shell. EXSYS Professional Linkable Object 

Modules give the advanced expert system developer the 

ability to create highly customized versions of the EXSYS 

Professional Runtime to meet special situations. Systems 

are developed with the normal EXSYS Professional 

Editor, and delivered with the highly customized runtime. 

To meet these needs, EXSYS is available as .obj modules 

(UNIX .o modules) that you can link to produce custom 

runtimes, or link into your applications. 

The EXSYS Professional Linkable Object Modules allow 

the developer to: 

• Call the EXSYS Professional inference engine 

as a C routine from within another program. 

• Add up to 100 user defined functions, which 

behave like internal EXSYS commands, to 

perform special functions for data acquisition 

or display. 

• Overlay EXSYS Professional with other 

programs which reduce the memory required to 

run large programs. 

• Combine the .RUL file, .TXT file and the 

EXSYS Professional inference engine into a 

single .EXE program. 

• Reduce the time needed to load external 

programs by linking them as internal routines. 

• Modify the start-up defaults to eliminate the 

need for a .CFG file. 

• Directly access the EXSYS Professional 

knowledge base data to read or write data from 

your routines or programs. 


• Change the default screens used to ask questions. 

• Disable particular unused functions which 

increases available memory and reduces 

program size. 

• Modify the link file to reduce program size, 

optimize for speed or modify the stack. 

• Change the formulas used to combine 

confidence in the Fuzzy Logic mode. 

The MS-DOS EXSYS Professional Linkable Object 

Modules include: 

• The Linkable Object Modules for the target 

operating system and compiler. 

• Default make and link files. 

• A source code for the start-up routines, and 

null routines that can be replaced with 

your custom routines. 

• Special routines to access EXSYS data 

structures or write data for use by the expert 

system. 

The GUI Linkable Object Modules (MS Windows, 

Macintosh, SUN Open Look, VMS/Motif and OS/2 

Presentation Manager) allow you to: 

• Create custom windows and dialogs. 

• Access the event stream. 

• Embed the inference engine within another 

GUI application. 

• Set up data exchange links with other programs. 

The expert systems created with Linkable Object Modules 

will work with the EXSYS expert systems you have 

already developed. In fact, these are the same object 

modules that were used to build EXSYS Professional. 

The developer must supply: 

• The appropriate C compiler (DOS, OS/2 - 

Microsoft C, VMS - VAX C, UNIX - default 

C compiler for target machine). 

• GUI versions require XVT Software, Inc.'s 

libraries. 

• The appropriate Linker (DOS - Plink86, others - 

default linker for target machine). 

Use of Linkable Object Modules requires an EXSYS 

Runtime license. The Runtime license allows distribution 

of customized systems produced with the Linkable Object 

Modules.

Interfaces 

Expert systems are powerful on their own, but many 

applications require integrating the expert system with 

other programs that you already use. EXSYS Professional 

has been designed to have a very open architecture and 

provide a wide range of interfaces into other programs. 

EXSYS Professional has many built-in functions which 

enable you to directly read or write data in many other 

popular programs and application formats. In addition, the 

EXSYS "RUN" command can call any program that you 

can run on your computer. 

Because EXSYS has such a wide range of interfaces, it can 

serve as a gateway between other programs that can not 

directly talk to each other. 

DATA B A S E S 

EXSYS Professional internal commands can read and 

write data from many popular databases. EXSYS 

Professional supports an SQL option which allows 

accessing data in many popular databases. SQL 

commands are handled through the command language. 

Connection to a SQL server, execution of an SQL 

command and processing of the data returned for 

assignment to an EXSYS variable is handled as procedural 

operations in the Command Language. You can write SQL 

programs that execute an SQL "Select" command that will 

return multiple data items. EXSYS Professional can step 

through and analyze the various records of returned data. 

Blackboards 

Report 

Generator 

Graphics 

Multimedia 

Neural 

Nets 

S p r e a d s h e e t s 

DDE 

Automatic 

Test 

Equipment 

Front End 

Programs 

EXSYS 

Inference Engine 

& Gateway 

MS-Windows MS-DOS 

Windows NT O S / 2 

Macintosh UNIX 

Open Look SCO UNIX 

VMS Motif V A X / V M S 

Data 

Tables 

SQL commands to write to the database or perform other 

database operations are also supported. EXSYS uses the 

Intersolv libraries for SQL database access and supports all 

SQL commands supported by Intersolv. 

The SQL databases supported include: 

ALLBASE INGRES 

Betrieve InterBase 

Clipper Microsoft SQL Server 

Database Manager NetWare SQL 

DB2 Oracle 

DB2/2 Paradox 

DB2/6000 PROGRESS 

dBase II, III, IV, V SQLBase 

Excel 5.0 SQL/400 

Excel .XLS files SQL/DS 

FoxBase Sybase SQL Server 

FoxPro Sybase System 

Gupta SQLBase Teradata 

IMAGE/SQL Text files 

INFORMIX XDB 

For simpler database access, there are other commands 

that perform direct read or write operations to some 

database files. Database calls can be executed from the 

Command Language or associated with data elements 

(qualifiers or variables). If a database call is associated 

with a variable, when the value or qualifier is needed, the 

database call will automatically be executed. 

External 

Programs 

Custom 

Commands 

Frames 

PI Plant 

Information 

System 

Linear 

P r o g r a m m i n g 

ANY 

Executable 

Program 

S Q L 

D a t a b a s e s 

Fuzzy 

Logic 

Custom 

Screens 


SPREADSHEETS 

EXSYS Professional supports reading and writing data 

from Lotus 1-2-3 spreadsheets. 

Spreadsheet calls can be executed from the Command 

Language or associated with data elements (qualifiers or 

variables). If a spreadsheet call is associated with a 

variable or qualifier, when the value is needed, the 

spreadsheet call will automatically be executed. 

LINEAR PROGRAMMING 

LINDO is a powerful linear and integer programming tool 

developed by LINDO Systems, Inc. and available on a 

wide range of platforms and operating systems. The 

integration of EXSYS Professional with LINDO enables 

you to incorporate non-numeric constraints and heuristics 

with LP optimization. EXSYS can analyze data before the 

linear programming model is built. It provides expert 

analysis of the linear programming results to makes 

important data available to end users untrained in 

interpreting LP results. 

Expert systems are powerful tools for expressing nonnumeric 

relationships, but they have lacked the specialized 

functions to handle optimization problems. Linear 

programs are excellent at optimization, but have difficulty 

incorporating non-numeric constraints and heuristics. By 

combining these two powerful technologies, you have a 

tool that can handle a much wider range of problems. 

The combination of EXSYS and LINDO provides a 

unique solution for real world problems such as: 

• LP applications delivered to end users not 

trained in interpreting LP results. 

• Automating frequently run LPs. 

• Complex LPs that require detailed 

interpretation. 

• LPs that require interaction with other programs 

or external data. 

• LPs that have constraints which can not be 

expressed numerically. 

• LPs that need graphical interfaces. 

• Expert systems that solve optimization problems. 

• Integration of PC based expert systems with a 

mainframe LP. 

The total EXSYS Professional user interface wraps around 

LINDO, allowing you to deliver complex, but easily 

usable applications. When data is needed from the user, 

the EXSYS user interface can ask for data with custom 

screens, graphics, custom programs, hypertext, or even 

speech and video. Data can be obtained from direct access 

to databases or spreadsheets, custom programs written in 

any language, frame based data representations, data 


tables, or any program that can be run on your computer. 

The results from LINDO can not only be formatted with 

the flexible EXSYS Professional Report Generator, but 

can be intelligently analyzed to produce the data 

interpretation that users want and need. 

The EXSYS / LINDO interface is particularly well suited 

for expert systems developed for scheduling, resource 

optimization, or other problems where an optimal solution 

must be found. The interface is designed to be easy and 

transparent to the end user. While the developer must 

understand both EXSYS Professional and LINDO to use 

the programs effectively, the end user is given 

recommendations and results without having to know 

either program. 

EXSYS Professional uses a technique similar to a report 

generator to create a LINDO model. This model is then 

run by LINDO automatically. The results of the LINDO 

run are read back into specified EXSYS Professional 

variables. 

EXSYS / LINDO SYNTAX 

The LINDO model syntax has been extended to allow the 

easy incorporation of EXSYS Professional variable values. 

It also supports the conditional inclusion of lines based on 

the values of variables. This allows a single model to be 

used for a wide range of problems. The basic syntax is: 

model commands 

~IF expression 


~ELSE 


~ENDIF 


~RESULTS 

data commands 

MODEL COMMANDS 

Model commands are lines of the LINDO model. EXSYS 

Professional variables and expressions are calculated and 

embedded in the model commands to incorporate data 

from the expert system. For example, the model 

command: 

MAX 2X+[NUM]Y 

would replace the EXSYS variable [NUM] with its value 

in the model. The value could have been calculated by the 

expert system or obtained through any of the EXSYS 

Professional interfaces. 

CONDITIONAL INCLUSION OF LINES 

When building the model, it may be desirable to include 

certain model commands ONLY if some criteria are met in 

the expert system. This is more effective and maintainable 

than having many LINDO model files. 

Lines can be conditionally included in the model with the 

~IF, ~ELSE and ~ENDIF commands. ~IF is followed by

any legal EXSYS Professional expression that evaluates to 

TRUE or FALSE. The expression can use numeric or 

string data, and utilize the logical inferencing capability of 

the expert system. 

For example, a part of a model might be written: 

MAX 2X+[NUM]Y 

ST 

~IF ([PRICE]

EXSYS/PI INTERFACE 

The Plant Information System (PI) from Oil Systems, Inc. 

is a powerful process data historian for VAX/VMS and 

Alpha computers. PI has the ability to monitor many 

process parameters and to maintain a historical record of 

the process data. 

PI is a powerful and effective way to collect and analyze 

numeric data. Data can be viewed in a wide variety of 

graphical displays to detect trends and problems. 

Historical data can be analyzed to determine the cause of a 

problem. 

The EXSYS/PI interface enables you to develop expert 

systems which can access the vast amount of historical PI 

data to determine the cause of a problem and what steps 

should be taken to correct it. 

EXSYS's interface allows the expert system to 

automatically get data from PI. This data may be 

combined with other non-numeric information asked of 

the user or obtained from other sources. The results of the 

expert system can be displayed to the user as 

recommended actions, or (with the correct hardware) 

action can be taken automatically. Data can be written 

directly back into the PI database. Best of all, the end user 

can ask the expert system "WHY" it is asking a question, 

or "HOW" it arrived at a particular conclusion. This both 

builds user confidence in the recommendations of the 

system, and simultaneously educates in the logic that was 

used. EXSYS incorporates Hypertext for even higher 

level help and explanation to users. Dynamic graphs of PI 

data can be displayed in EXSYS Custom Screens. 

PI provides a wide range of analytical tools through 

performance equations, but when even more power is 

needed, an expert system is an ideal solution. EXSYS 

Professional combines sophisticated mathematical 

functions, non-numeric heuristics, IF-THEN-ELSE rules, 

frames and a procedural command language to build 

expert systems for complex real-world problems. The PI 

performance equations allow you take PI data, 

arithmetically manipulate it and write it back into PI tags. 

EXSYS allows you to take PI data and perform complex 

numeric and non-numeric analysis with the rules in an 

expert system, and write data back to a PI tag. Also, since 

the EXSYS rules are easy to read and understand, system 

maintenance problems are reduced. 

The expert system's capability offered by EXSYS 

Professional is also a gateway from PI to a wide range of 

other EXSYS interface programs including: linear 

programming, data bases, spreadsheets, custom screen 

languages, user defined functions, data tables and frames, 

neural nets, and much more. The gateway provided by 

EXSYS Professional opens up an enormous variety of 

possibilities for analysis and presentation of PI data. 

EXSYS uses PI syntax and commands to make data 

acquisition from PI as easy as possible. As PI data 

acquisition commands are entered in EXSYS, they are 

automatically checked for syntactical correctness with 

existing PI tags and time formats. Direct access from the 


expert system to the PI logger and message facility allows 

expert system recommendations to be automatically sent 

to the people that need the data over the PI network, and in 

the form that PI users expect. 

The EXSYS/PI interface has been developed in close 

cooperation with the staff at Oil Systems, Inc. to provide 

the features and capabilities needed in real-world 

situations. 

EXSYS expert systems can be used to handle a wide range 

of tasks: 

• EXSYS can assist an operator in bringing a 

process that is operating outside of the desired 

parameters, back within parameters. A frequent 

problem is to over compensate and put a process 

into oscillation about the desired setting. An 

EXSYS expert system can recommend the 

necessary steps to bring the process in 

asymptotically. 

• EXSYS can capture and disseminate the skills 

of your best people. Often one operator will get 

significantly better performance than others. 

Having that person build a simple expert system 

makes their skill available to others and codifies 

their decision making process. 

• EXSYS can run in the background and monitor 

for developing problems or dangerous 

situations. This is especially useful in 

monitoring for rarely occurring problems 

which an operator may not notice. 

• EXSYS can be used to provide assistance in 

performing infrequently done operations such 

as starting up a piece of equipment. 

• EXSYS can monitor compliance with 

regulations, including those of ISO 9000. 

• EXSYS coupled with linear programming, 

can handle scheduling changes based on 

day-to-day operations and problems. 

• The EXSYS/PI interface is available for 

VAX/VMS, and can be run on terminals as 

simple as a VT-100. The interface is available 

in more sophisticated and easy to use 

VMS/Motif and Alpha/Motif versions, and for 

MS-Windows computers communicating to the 

VAX through Pathworks. 

OTHER PROGRAMS 

In addition to the interfaces built into EXSYS, you can 

call any program which you can run on your computer. 

EXSYS has an internal RUN(... ) command. Whatever 

command is put in the ( ) will be executed as if it was 

entered from the operating system command line. This 

enables you to run any program.

In addition to calling the program, you can pass EXSYS 

data to the called program as command line arguments or 

in data files. The technique has been kept as generic and 

flexible as possible. For example: 

RUN(myprog [X] 1 "ABC" /C) 

EXSYS would call the program myprog and pass it the 

current value of the variable [X], the value 1, and the 

string "ABC". If you did not have the /C, the data would 

be written into a file that could be accessed by the called 

program. 

Likewise, the called program may need to return data to 

EXSYS. All the program has to do is write an ASCII file 

in a simple format containing the data. When the called 

program terminates, EXSYS automatically reads the data 

in this file. 

Using EXSYS Linkable Object Modules, more complex 

techniques for inter-process communication can be 

implemented such as pipes or DDE. 

EXSYS Company History 

EXSYS Inc. was founded in 1983 to market expert system 

development tools to the MS-DOS market. The goal was 

to produce an expert system development tool capable of 

being used by people with no A.I. training. To achieve 

this, it was necessary to design a tool that was 

conceptually as easy to use as a word processor, but 

capable of handling complex decision making problems. 

It was believed that given this sort of tool, domain experts 

could build expert systems themselves. 

EXSYS did not follow the traditional form of most 

academic AI tools. Easy-to-use functionality was 

emphasized over the standard academic knowledge 

representation techniques. The developers at EXSYS felt 

that while some complex techniques used in academic 

systems were certainly valid, they were not needed for 

most real-world applications and included only those 

functions that actually helped get systems built. Complex 

algorithms that were rarely needed were not used. 

The result was a program that was easy-to-use, could be 

learned in a few days, and had more than enough power to 

handle most real-world problems. Standard EXSYS, the 

first EXSYS expert system shell, was introduced in 1983. 

Users soon discovered that Standard EXSYS had 

sufficient power for their applications, was much easier to 

learn than other tools and much lower in cost. 

EXSYS Inc. has always had a very strong philosophy of 

listening to its users. When users requested new features, 

if possible, they were incorporated into the program. 

Using this approach, Standard EXSYS grew in power in 

the areas where users actually needed it. Complex 

features were only added when there was a need for them, 

not added just for the sake of adding them. All new 

features had to produce real benefits for actual users. 

Due to user requests, in 1986 it was decided to port 

Standard EXSYS to DEC VAX computers and in 1987, to 

the UNIX platform. The EXSYS C source code is very 

generic and portable. Ports were done for a wide variety 

of UNIX computers and several foreign languages. 

By 1988, thousands of applications had been developed 

using Standard EXSYS. It had been used successfully for 

a very wide range of problems. However, there were still 

some problems that were difficult to handle. Users 

requested a more powerful program that could handle 

these problems, but which was still easy to use. 

To meet these requests, EXSYS Professional was 

developed. This was a significantly more powerful 

program, however the EXSYS philosophy of keeping the 

program easy-to-use was maintained. EXSYS 

Professional added many options for the user. If special 

features were needed in a particular area, they were 

available. The most powerful feature added was the 

Command Language which enables EXSYS Professional 

to handle a much wider range of problems than the 

original Standard EXSYS. 

In 1991 the entire EXSYS Professional developer and user 

interface was rewritten to take advantage of the many GUI 

(Graphical User Interfaces) platforms that had become 

popular. EXSYS Professional was ported to MS 

Windows, Windows NT, Macintosh, Sun Open Look, 

VAX/Motif and OS/2 Presentation Manager. The new 

GUI versions made expert system development faster than 

ever before and opened many new possibilities for the user 

interface options. 

In 1993 EXSYS RuleBook was developed to make it very 

easy to build applications where the logic could be 

represented as a tree diagrams. This covers a very wide 

range of problems, and produced a tool that could be very 

rapidly learned. 

In 1995, user requests lead EXSYS to add fuzzy logic to 

EXSYS Professional. As with other complex areas, the 

portion of fuzzy logic that is really useful and which can 

be easily understood was incorporated into the tool. This 

make fuzzy logic approachable and easy to use. 

EXSYS tools have continued to grow in features and 

capability. EXSYS, Inc. has a proven willingness to 

respond to the needs of its users. 

For more information contact: 

EXSYS, Inc 

1720 Louisiana Blvd. NE, Suite 312 

Albuquerque, NM 87110 U.S.A. 

TEL (505)256-8356 

FAX (505)256-8359 


ACCOUNTING & FINANCE - Cost Code Selector, Stock & 

Commodity Trading, Portfolio Construction, Home Purchasing, 

Financial Planner Training and Selection, Personal Tax Advisor, 

Detecting Insider Trading, Organizational Services, Credit 

Analysis Advisor, Bank Loan Identification, Credit Control, 

Loan Documentation, Assessment of Risk and Fraud in Financial 

Institutions, Aid in Tax Form Completion, Commercial Loan 

Approval Predictor... 

A C T I V I T I E S - Aquarium Water Quality Analysis, Bridge 

Opening Bid Advisor, Bird Identification, Sailing Tactics, 

Weaving Trainer... 

A G R I C U L T U R A L - Irrigation and Pest Control, Crop Variety 

Selection and Management, Soil Characterization and Utilization 

for Specific Areas, Fertilizer, Climate and Soil Interaction and 

Analysis, Salmon Stocking Rates and Species Selection, Forest 

Inventory, Weed Identification, Soil Conservation, Tree Selection 

Based on Environmental Conditions, Planning and Design of 

Agroforestry Systems... 

B U S I N E S S - Alternatives for Fragmented Industry, Advertising 

Copy Development, Shipping Documentation and Routes, Market 

Advisor for Process Control Systems, Demographic and Market 

Assessment, Product Performance Trouble-shooting, Sales 

Personnel Assessment, Account Marketing, Invention Patent 

Ability, Salary & Benefit Planning, Client Profile Business 

Application Selection, Professional Service Selection, Career Goal 

Planning, Pension Fund Calculator, Unemployment Insurance 

Eligibility... 

C H E M I C A L - Hazard Evaluation, Chemical Facilities 

Procedures, Correct Propellant Ingredient Mixture, Pollution 

Control Technology Permits, Common Metal and Alloy 

Identification, Real-time Process Controlled City Waste Water 

Management, Solvent Selection for Chemical Compounds, 

Pottery Glaze Recipe and Identification, Pulp Bleaching Advisor, 

Toxicity of Laboratory Chemicals, Lime Recognition System, 

Process Diagnosing and Troubleshooting... 

C O M P U T E R - Software System Diagnostic Modeling, 

Application Sizing, Software Quality Assurance, Program 

Classification, Locating Component Failure & Analysis, New 

Technology Selection, Training Systems, Custom Hardware 

Diagnostics, Decision Support Systems, MIS Support System, 

Program Library Maintenance, Fault Detection and Diagnostics 

of Wide Area Networks, Analysis of Statistical Data, Personal 

Computer Configuration, Shielding Technique Selection, 

Database Design, Computerized Technical Service 

Representation, Hardware and Software Selection by Non 

Technical Users, New User of Computer Assistance, 

Documentation Recommendations to Users, Monitoring, Repair 

Assistance and Problem Prediction of Operating System... 

C O N S T R U C T I O N - Pavement Rehabilitation & Design, 

Structural Damage Assessment, Equipment Evaluation & 

Selection, Material Costing & Selection, Project Scheduling, 

Cost Estimating, Evaluating Multifamily Housing Projects, Work 

Zone Safety Trainer/Advisor, Weld Procedure Selection and 

This document and any examples contained herein are provided "as is" and are subject to change without notice. 

EXSYS,Inc. makes no warranty of any kind with regard to this document, including, but not limited to, the 

implied warranties of merchantability and fitness for a particular purpose. EXSYS, Inc. shall not be liable for any 

errors or for incidental or consequential damages in connection with the furnishing, performance, or use of this 

document or the examples herein. 

© 1995 EXSYS, Inc. All rights reserved. July 1995 

Printed and bound in the United States of America 

Expert System Applications 

All other product names are copyright and registered trademarks/tradenames of their respective owners. 

Cost Estimating, Soil Compacting, Fire Code Advisor, Alarm 

Management System... 

EDUCATION - TRAINING - Library Reference Material 

Recommendation, Interpretation of Statistical Quality Control 

Data, Teaching Mineral, Rock and Fossil Identification, Student 

Financial Aid Eligibility, Analysis of Metal Cautions, Fire 

Department Emergency Management Advisor, Medical Student 

Diagnostic Systems, Dentistry Advisor, Telephone Customer 

Support Instruction, Gas Turbine Training, Industrial Training, 

Patient Care Advisor for Student Nurses... 

ENGINEERING - INDUSTRIAL - Engineering Change 

Control Demonstrating, Diesel Engine Lube Oil Wear Analysis, 

Superalloys Phase Analysis, Equipment Diagnostics, Electronic 

Semiconductor Failure Testing, Parts List Selection & Sizing, 

Power Generation System Scheduling, Component Failure 

Prediction, Machining Advisor, Numerically Controlled Machine 

Tool Selection, Petrochemical Plant Process Control, Control 

Panel Layout Design, Material and Process Design Advisor... 

I N S U R A N C E - Rating for Substandard Life Insurance, Workers 

Comp Classification, Underwriting Assistance, Social Security 

Help Desk and Benefit Identification, Unemployment Insurance 

E l i g i b i l i t y . . . 

M E D I C A L - Admission Protocols, X-Ray Analysis, 

Hematological Diagnoses, Psychiatric Interviewing, Pediatric 

Auditory Brainstem Response Interpretation, Medical Decision 

Making, Respirator Selection for Preschool Children, Health 

Services Utilization and modeling, Diagnostic Systems, In-Vitro 

Fertilization, Symptom Analysis, Voice-Driven Lab Diagnosis, 

Rehabilitation Feasibility Strategies, Billing and Account 

Management, Disease Research... 

MILITARY , GOVERNMENT & SPACE RELATED - 

Submarine Approach Officer Training, Combat Methodology 

Selection, Radar Mode Workstation Designing, Federal Contract 

Management, Severe Weather Forecasting, Shuttle Payload On- 

Orbit Analysis, Metals Materials Selector, GB Satellite 

Abnormality Correction, Selection of Non-materials in 

Aerospace Applications... 

T R O U B L E - S H O O T I N G - Airplane Starting Systems, Data 

Communications, Test and Repair of a PCB, Gas Turbine 

Control System, Bearing System Failures, Telecommunications 

Difficulties, Real-Time Process Control, Meterman's Assistant 

System, Mechanical Equipment and Systems Diagnosis, Weld 

Flaw Detection, Web Break Diagnosis in Paper Milling, Power 

Plant Turbine Generator Bearing Maintenance System... 

MANY, MANY OTHERS - Telephone System Configurator, 

Training Material & Product Selection, Manufacturing Resource 

Planning, Production Scheduling, Service Networking, Airline 

Scheduling, Cost/Benefit Analysis, Planning Implementation, 

Career Development, Quick Proposal Estimating, Credit Control, 

Product Development, Telephone Call Screening, Real Estate 

Market & Mortgage Credit Analysis, Retirement Planning, Sales 

Analysis... 

EXSYS, Inc. 

1720 Louisiana Blvd. NE 

Suite 312 

Albuquerque, NM 8711 

TEL(505)256-8356 

FAX(505)256-8359

EXSYS Professional Developer Interface

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