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EXSYS® Professional Getting Started Manual
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Getting Started with EXSYS
First a Few Terms
Before you start building systems, there are a few terms you need to know. EXSYS Professional expert systems are made up of individual facts that represent pieces of decision-making knowledge. These individual facts are called RULES. The rules are in anIF-THEN form. A rule may also have an ELSE part, (IF-THENELSE) but IF-THEN is more common. In real life, IF-THEN rules are used all the time. They are the way a person thinks and are the way you describe your decision-making steps. To run the rules and reach a conclusion, data is required. This data comes from user input and data the system “knows” from rules. EXSYS tests the IF parts of rules to seeif the rules are true. When the IF part of a rule is determined to be true, the THEN part is assumed to be true and added to the facts that the system knows. EXSYS uses two types of data: QUALIFIERS which allow the user to select one (or more) values from a pre-defined list of values. VARIABLES which allow the user to input any numeric or string value.
IF it is raining, THEN take anumbrella. IF the light is out, THEN check the power switch.
Expert systems usually are designed to arrive at a conclusion or recommendation. In EXSYS, these possible recommendations are called CHOICES. There are typically many possible choices in an expert system, and the rules will select which is appropriate for a particular set of input data. In the examples above,"take an umbrella" and "check the power switch" could be choices. Getting Started with EXSYS® Professional
Rule IF Part
Rule Then Part
Getting Started with EXSYS
Some examples of qualifiers are: The weather today is 1 Sunny 2 Cloudy 3 Raining 4 Snowing The light is 1 ON 2 OFF Qualifiers are very useful in building expert systems because they allow the possible input values to bespecified. This makes for faster and easier system development. However, the lists must be complete enough to handle all possible situations. In the example, if the weather is actually foggy, the user would be forced to select "cloudy" or "raining". Some examples of variables are: The voltage at point A Your name The current price of gold There are many other terms that will be used later, but thisis enough to get started. Getting Started with EXSYS® Professional Variables can have any value and may be numeric or string. It is not necessary to create pre-defined lists of possible values. Variables are used two ways in expert systems: 1. Tested in the IF part by being included in a boolean expression. For example, IF The voltage at point A is less than 1.5 volts THEN Replace the battery2. Assigned a value in the THEN part. For example, IF The the ice cream is melting THEN Set the temperature to 25 degrees
Lesson 1: Building a Simple Rule
or How Many Knowledge Engineers Does It Take To Change a Light Bulb?
Suppose a light that was on in your office suddenly goes out. You might decide to change the bulb. You are going to write an expert system to capture this profound...