4. METHODS
Algorithm to Calculate PCL measure
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To evaluate PCL measure, a procedure progression of an operator and a standard procedure progression that should be progressed in typical situations are received as inputs. The standard procedure progression is obtained by relevant procedure and the record of status in the situation.
Algorithm to Calculate VPP measure
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The method used to measure a VPP score consists of two stages: generating a directed acyclic graph from human performance records and computing the complexity of the graph. First, the sequences of steps that the operators have performed are obtained. The partial-order alignment (POA) algorithm transforms the step sequences into a directed acyclic graph using a similarity score matrix. The similarity score matrix is numerically assessed data to define how similar each step is with the others. The POA algorithm aligns the steps of a sequence with similar steps of another sequence. For this sequence alignment, the POA algorithm uses the Smith-waterman algorithm to maximize the total similarity of the aligned sequence using a dynamic programming method. The POA then fuses the aligned steps and connect them. After a directed acyclic graph for two sequences is generated, the POA attempts to align and fuse the graph with the other sequence.
Second, the graph complexity is calculated for the finally generated graph from the first stage. This graph complexity becomes a VPP score of the obtained data, because the more the variably procedures are progressed, the more complex the generated graph becomes. To calculate the graph complexity, a technique to measure the information entropy-based complexity was employed. In a generated graph by POA, there are V vertices, which are procedural steps. When an edge E{i,j} is the link from vertex i to vertex j, we can assign a certain weight to each of the edges. The graph complexity for vertex i is an entropy to select an edge among edges emanating from step i. Undoubtedly this complexity means a VPP score of step i. A VPP score for a certain task, which includes one or more steps, is obtained by summing the graph complexity of the relevant steps.
