In the second stage, the rule set for the PSSI Rule was developed. The PSSI Rule has several rules that are used to perform PSSI calculations and to obtain recommendations to minimize discomfort and muscle fatigue based on the PSSI value. The development of the PSSI Rule value. The development of the PSSI Rule began with assigning the results of risk factor analysis (in terms of risk levels) to multipliers to represent their severity for discomfort and fatigue. A PSSI value is obtained through multiplicative interactions between these multipliers. Potential solutions to minimize the risk levels were then recommended based on the PSSI value. Table 2 summarizes the knowledge base of the DSSfPS model, which includes the risk factors or knowledge, knowledge description, numbers of rules, questions, and alternative answers.