4.2.1. Knowledge Acquisition

"The knowledge acquisition process includes extracting, transforming, and validating expertise from di fferent information sources for developing a knowledge base repository" [23]. The knowledge used in this research consists of "general knowledge" and "process-specific knowledge". In this study, to assist the fault diagnosis process, "Western Electric" [44] tests were utilized as general knowledge, and, to gather process-specific knowledge, "cause and e ffect (Ishikawa diagram)" [41] diagrams were prepared to investigate the root-cause. Using cause and e ffect diagrams, the most problematic reasons in the plaster production process were systematically determined (Figure 9). Next, failure modes and effects analysis (FMEA) (Table 9) was applied as an analytical method that incorporates the technology and experts' knowledge in identifying and prioritizing foreseeable failure modes of the process in order to eliminate or reduce their occurrence [42]. Finally, FMEA analysis results were collected in the knowledge base with the aim of making a complete reference for future issues. As can be seen in Table 9, FMEA uses the risk priority number (RPN) to evaluate the risk level of the process. RPN is calculated by multiplying the scores of three risk factors named occurrence (O), which is the frequency of the failure, severity (S), which is related to the e ffect of disruption on the system, and detection (D), which refers to the probability of detecting the failure. FMEA uses five scales or scores (1–5) to measure these factors.

 **Figure 9.** Cause and e ffect diagram: (**a**) for increase of crystal water; (**b**) for decrease of crystal water.


**Table 9.** Failure modes and effects analysis (FMEA) form for the critical parameter (crystal water).
