EXSYS Professional Developer Interface

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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 THE EXSYS DEVELOPER OVERVIEW • 3
Page 1 and 2: Expert System Software THE EXSYS ®
Page 3: E xpert knowledge is often scarce a
Page 7 and 8: While only a small part of the comm
Page 9 and 10: Expert - Checks the system for logi
Page 11 and 12: Qualifier Select qualifier by text
Page 13 and 14: EXSYS RuleBook PLUS RuleBook PLUS u
Page 15 and 16: IF [INPUT TEMP] > 160 and [INPUT TE
Page 17 and 18: In EXSYS Professional, to make a qu
Page 19 and 20: For example, suppose a system uses
Page 21 and 22: SCREEN TEMPLATES Custom screen temp
Page 23 and 24: Interfaces Expert systems are power
Page 25 and 26: any legal EXSYS Professional expres
Page 27 and 28: In addition to calling the program,

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