tokens: Along with the dataset , the authors propose three incremental learning scenarios : ( i ) new instances ( NI ) where all classes are shown in the first batch while subsequent instances of known classes become available over time , new classes ( NC ) where , for each sequential batch , new object classes are available so that the model must deal with the learning of new classes without forgetting previously learned ones , and ( iii ) new instances and classes ( NIC ) where both new classes and instances are presented in each training batch .