  Using the sine-Gordon model as the prime example an alternative approach to
integrable boundary conditions for a theory restricted to a half-line is
proposed. The main idea is to explore the consequences of taking into account
the topological charge residing on the boundary and the fact it changes as
solitons in the bulk reflect from the boundary. In this context, reflection
matrices are intrinsically infinite dimensional, more general than the
two-parameter Ghoshal-Zamolodchikov reflection matrix, and related in an
intimate manner with defects.
