5
Functional Dependence
Functional dependence takes place when the malfunction of one system component (referred to as the trigger) causes other components (referred to as dependent components) within the same system to become unusable or inaccessible. For example, in a computer system, peripheral devices such as keyboards and monitors are accessed through I/O controllers. If the I/O controller malfunctions, the peripheral devices connected to it become unusable [1]. In other words, the peripheral devices have functional dependence on the I/O controller. Another example is a computer network system where a computer can access the Internet or communicate with other computers through routers [2]. The router is the trigger component, and computers connected to the router have functional dependence on the router.
The functional dependence behavior is modeled via Functional DEPendence (FDEP) gates in the dynamic fault tree (DFT) analysis [3,4] (Section 2.3.2). Note that the FDEP gate has...