  We generalize the idea of boundary states to open string channel. They
describe the emission and absorption of the open string in the presence of
intersecting D-branes. We study the algebra between such states under the star
products of string field theory and confirm that they are projectors in a
generalized sense. Based on this observation, we propose a modular dual
description of Witten's open string field theory which seems to be an
appropriate set-up to study D-branes by string field theory.
