A particular case is defined to cover specified problem domain. Then, symptoms that are likely to occur and its diagnosis results are defined in that problem domain. Symptoms definition processes are followed by several questions to identity some facts that occur. Diagnosis result definition processes consist of conclusion statements and given solutions or suggestions. After symptoms and its possible diagnosis are defined, knowledge engineers are able to construct rule structure into a decision tree that consists of several linked nodes. Figure 6 illustrates an application form for constructing the rule base.