A 
system for the representation, editing, evaluation, and 
inference of graphical models is disclosed which can be used to construct and evaluate a 
graphical model or graphical network and to calculate 
inference values. An efficient method of updating graphical models is demonstrated, and provides the basis for an improved 
system for manipulation and evaluation of probabilistic models. The graphical network editor is useful in the construction of graphical 
modes such as Bayesian Networks. The graphical network and network 
graphical user interface (GUI) are used in conjunction with each other to model a 
system wherein failure probabilities and the current state of components are taken into account to monitor the health and progress of a system for an engineer or 
engineering software to evaluate and monitor. The evaluation is useful in the monitoring of assets and other 
real systems having multiple, dependent, and independently operating components such as a pump, a manufacturing 
plant, a 
production line, an 
assembly line, where asset health and 
quality control is a concern. The asset components each influencing some overall outcome of a system or situation. Success or failure or 
probability of success, 
probability of failure and health of the system can be monitored and manipulated by altering the values of 
prior probability and 
posterior probability values. Failure correlation between components can be evaluated wherein failure rates of asset is unknown. Production and quality can be monitored and altered.