  After reviewing D-branes as conjugacy classes and various charge
quantizations (modulo $k$) in WZW model, we develop the classification and
systematic construction of all possible untwisted D-branes in Lie groups of
A-D-E series. D-branes are classified according to their positions in the
maximal torus. The moduli space of D-branes is naturally identified with a unit
cell in the weight space which is exponentiated to be the maximal torus.
However, for the D-brane classification, one may consider only the fundamental
Weyl domain that is surrounded by the hyperplanes defined by Weyl reflections.
We construct all the D-branes by the method of iterative deletion in the Dynkin
diagram. The dimension of a D-brane always becomes an even number and it
reduces as we go from a generic point of the fundamental domain to its higher
co-dimensional boundaries. Quantum mechanical stability requires that only
D-branes at discrete positions are allowed.
