P: plan d: do c: check a: action processing This is the so-called "pdsa", which is a cyclical process. From the plan to the result, if there are good results, continue to promote them, and if there are bad results, correct them. It is a spiral rising process, generally speaking, it develops in the direction of Pareto optimality. Process method is the process of transforming input into output by using various resources. PDCA is a kind of process management in a sense.