2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/55310We 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 ωof the fusion rules that preserves conformal weights. Non-trivial automorphisms ωcorrespond to D-brane configurations for arbitrary conformal field theories.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 1997High Energy Physics - Theorytext