 The advantage of this type of model is that arbitrary features (i.e.functions) of the observations can be modeled, allowing domain-specific knowledge of the problem at hand to be injected into the model.Models of this sort are not limited to modeling direct dependencies between a hidden state and its associated observation; rather, features of nearby observations, of combinations of the associated observation and nearby observations, or in fact of arbitrary observations at any distance from a given hidden state can be included in the process used to determine the value of a hidden state.