Task and Procedure Level Primitives for Modeling Human Error

In this paper, we describe the development of behavioral primitives for use in human reliability analysis (HRA). Previously, in the GOMS-HRA method, we described the development of task level primitives, which model basic human cognition and actions. Like generic task types found in some HRA methods, the task level primitives provide a generic or nominal human error probability. These generic task types are often modeled at the task level—grouped according to a high-level goal that includes many activities. In contrast, task level primitives represent a finer level of task decomposition, corresponding not to a group of actions that comprise an overall task but rather individual steps toward that task. In this paper, we further elaborate on the task level primitives by grouping task level primitives into procedure level primitives. This terminology reflects standard groupings of activities that are performed by reactor operators when following operating procedures. For the purposes of HRA, it is desirable to model operator actions according to these prescribed procedure categories. We present mappings of the procedure level to the task level primitives found in the GOMS-HRA method. We provide examples and conclude that procedure level primitives are a useful tool to streamline HRA modeling and quantification, especially for dynamic HRA applications.