We outline the structure of boundary conditions in conformal field theory. A
boundary condition is specified by a consistent collection of reflection
coefficients for bulk fields on the disk together with a choice of an
automorphism \omega of the fusion rules that preserves conformal weights.
Non-trivial automorphisms \omega correspond to D-brane configurations for
arbitrary conformal field theories.Comment: 7 pages, LaTeX2e. Slightly extended version of a talk given by J.
Fuchs at the 31st International Symposium Ahrenshoop on the Theory of
Elementary Particles, Buckow, Germany, September 199
