1. A Markov model discriminator system comprising: means for providing an input sequence to be classified; means coupled to said means for providing an input sequence for performing two different model likelihood calculations based on two different Markov model parameters representing two different classes of examples, each class having a predetermined characteristic on which discrimination between classes is based; means for comparing said likelihood calculations as to which of said characteristics said input sequence is likely to exhibit based on said comparison, thus to classify said input sequence; and means for training said means coupled to said input sequence for performing said two calculations by generating said Markov model parameters taking onto account both negative and positive examples of said different classes.