Application of functional models to system design, operation, and performance assessment

A variety of modeling techniques have been developed to assess human performance in complex systems. For example, logic models such as fault trees and event trees have been used to incorporate human performance in risk assessments for complex systems. These methods are based on an event-oriented perspective because they illustrate the different events that occur in system operation. An alternative modeling perspective, the function-oriented approach, is less often used for system modeling. Function oriented methods illustrate the critical functions that must be performed to successfully complete the mission of the system, and the resources that can be used to maintain the critical functions. Functional modeling techniques have certain advantages for many applications, and have the potential to form a consistent framework for modeling human performance throughout the system lifecycle. This paper describes function-oriented modeling methods that have been developed at the Idaho National Engineering Laboratory (INEL), and how they have been applied to the assessment of human performance for a variety of complex systems