*BibTeX entry*@INPROCEEDINGS{CGQ93a, author={G. Cohen and S. Gaubert and J.P. Quadrat}, title={From first to second-order theory of linear discrete event systems}, booktitle={12th IFAC}, address={Sydney}, month={Jul.}, year={1993}, }

*Abstract*For timed event graphs, linear models were obtained using dioid algebra. After describing backward equations which solve an optimal tracking problem and which introduce co-state variables, this paper presents preliminary results concerning the matrix of `ratios' (i.e. conventional differences) of co-states over states: this matrix sounds like a Riccati matrix, although a neat analogue to a Riccati equation has not been found yet.