Time Variable

The time variable is a parameter variable that represents the time and that can be used in the formulas describing probability distributions. This variable is activated by using the contextual menu associated with the background of the graph panel. Its value, that is always observed, is a positive integer that corresponds to the value of the current time step of the dynamic Bayesian network (the value that appears in the time meter in Validation mode).

This is not a classical Bayesian network variable. It can be used in the formula of any node if it is activated. The corresponding probability tables don't reference it explicitly. There are only the probability values that depend directly of its value. The graphical indicator located in the status bar of the network's window indicates only that it is possible to use this variable :

During the temporal inference, after each time increment, the probability distributions described by the equations that use this parameter are updated. Note that in Modeling mode, its value is set to zero (the resulting probability tables are then computed by replacing t with zero)

The use of this parameter transforms the network into a dynamic Bayesian network.