Two components of the boundary of \(\text \textbf{I}_3\). (Deux composantes du bord de \(\text \textbf{I}_3\)) Singularités de bord: Dualité, formules de Picard Lefschetz relatives et diagrammes de Dynkin. (Singularities with boundary: Duality, relative Picard Lefschetz formulas and Dynkin diagrams) 