Online one-class classification Dr. David M.J. Tax Fraunhofer FIRST.IDA Kekulestr.7, D-12489 Berlin Germany Abstract In recent years the problem of one-class classification is recognized as a new field of research. In constrast with normal classification problems where one tries to distinguish between two (or more) classes of objects, one-class classification tries to describe one class of objects, and distinguish it from all other possible objects. This can be used in novelty detection (for machine condition monitoring where faults should be detected), outlier detection (for more confident classification) or in badly balanced data (classification in medical data with poorly sampled classes). In my talk I will present an online version of a one-class classifier, the Support Vector Data Description (SVDD), a classifier inspired by the support vector machines. By using an online SVDD, dynamically changing data can be followed in time and outlier objects can be detected. I will show some preliminary results on the processing of EEG monitoring data.