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Modèles Informatiques du Langage et de la Cognition - MILC

Artificial Intelligence Group
Computer Science Department

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Denis BONNET

Ph.D. Student

Biography

Born August 2nd 1970 at Talence (Gironde, France).
Education : Engineer at E.N.S.T. (1991-1994).
Five months internship in the AI department of the Regie Renault on the forecasting of time series with neural networks (quarterly forecasting of the number of car sales in France). For more details, you can have a look at my resume in postscript format (in french).

Research

Thesis director : Alain Grumbach
Research Group: MILC
Laboratory : SNCF, Direction de la Recherche, Département Prospective
Intended examination date : November 1997

A connectionnist Approach to Time Series Forecasting

Nowadays, classical connectionnist techniques are very well-known, particularly in the field of MultiLayers Perceptrons (MLP). Nonetheless, time series predictions using MLP are quite difficult and results are not as good as they were supposed to be. In fact, time series do not accomodate very well with neural networks because of : The aim of this Ph.D. is to design a methodology for this kind of neural networks based forecasting, to find architectures which are suitable for some kind of prediction (FIR, TDNN, RST,... , hybrid ones), or design new ones, and finally to design tests which may be used to compare our results with statistical models.

Another part of our work is to find a new architecture dedicated to time dependant series, that is to say a neural network architecture where time will not be another spatial dimension. Opposed to TDNN, we want time to be a built-in dimension. A first attempt in this direction is the delta-NARMA neural network, which can be seen as a connectionist extension of ARIMA and ARARMA statistical models.

Another topic of interest for us is the fusion between symbolic and numerical processing in the particular case of time series prediction. We study both the use of classical statistical methods (Fischer statistic) and connectionist one to estimate relevance and redundancy. We also study from a more general point of view how to handle symbolic data with a classical connectionist network.

To implement delta-NARMA neural networks and to make experiments about the fusion of symbolic and numerical processing, we have developped a simulator: dnns. A course for 3rd year ENST student I wrote on time series prediction using neural networks is available here (in french, compressed postscript, 683K).

Papers

Last changes March 7 1997
Denis Bonnet (bonnet@inf.enst.fr)