Java-Based Expert Systems — JESS

Each JESS rule engine can incorporate a series of facts, which are stored in the working memory. Rules react to additions, deletions, and changes to the working memory. JESS distinguishes between pure facts, which are defined by JESS, and shadow facts, which are connected to Java objects. 

Facts are based on templates, similar to Java classes, which consist of a name and a series of slots that represent the properties of the class. A definition of a template might look like this  

A fact is then defined by nsing the (assert) command  

Using a shadow fact that derives from a Java class called Molecnles reqnires a reference to this class in the template  

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There are several categories of expert systems, but by far the most popular are the rule-based expert systems. Most rule-based expert systems are created with an expert system shell. The first successful rule-based expert system shell was the OPS 5 of Digital Equipment Corporation (DEG), and the most popular modern systems are CLIPS, developed by the National Aeronautics and Space Administration (NASA) in 1985, and its Java clone, Jess, developed at Sandia National Laboratories in 1995. All rule-based expert systems have a similar architecture, and the shells make it fairly easy to create an expert system as soon as a knowledge engineer gathers the knowledge from a domain expert. The most important component of a rule-based expert system is its knowledge base of rules. Each rule consists of an if-then statement... 

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