SAMPLE is the most recent version of a line of models that began with the procedure oriented crew (PROCRU) model. SAMPLE and its antecedents have been used to represent individual operators, as well as crews of complex human-machine systems (Baron et al., 1980; Zacharias et al., 1981, 1994, 1996). The following discussion takes a general perspective, and not all of the characteristics described apply to every variant.

SAMPLE and its antecedents have been used in the examination of crew procedures. Some variations are used to model single operators. Variations of SAMPLE have been used in analysis of the approach to landing procedures of commercial transport aircraft (PROCRU), analysis of antiaircraft artillery system procedures (AAACRU), evaluation of nuclear power plant control automation/decision aiding (crew/system integration model [CSIM]), and air combat situation awareness analysis. Most recently, SAMPLE has been used to evaluate air traffic alerting systems in a free flight environment.

Assumptions basic to SAMPLE are that the behavior of the crew (in some cases an individual operator) is guided by highly structured, standard procedures and driven by detected events and assessed situations. Some variants assume a multitasking environment, though this aspect is less emphasized in the later model. In all cases, however, the crew is concerned primarily with performing situation assessment, discrete procedure execution, continuous control, and communication.

The SAMPLE architecture consists of a system model and one or more human operator models.

The system model includes system dynamics (e.g., ownship, the plant, or a target), which are modeled by partial differential equations of motion (e.g., point mass equations for vehicle trajectory). The system dynamics can be modeled at any level of complexity desired.

A human operator model exists for each crew member. It consists of sensory and effector channels and several processors.

The sensory channels model visual and auditory sensing. Both are based on an optimal control model with no perceptual delay. They model limitations due to observation noise and stimulus energy with respect to defined thresholds. All