  We present the basic ingredients of continuum optomechanics, i.e. the
suitable extension of cavity-optomechanical concepts to the interaction of
photons and phonons in an extended waveguide. We introduce a real-space picture
and argue which coupling terms may arise in leading order in the spatial
derivatives. This picture allows us to discuss quantum noise, dissipation, and
the correct boundary conditions at the waveguide entrance. The connections both
to optomechanical arrays as well as to the theory of Brillouin scattering in
waveguides are highlighted. We identify the 'strong coupling regime' of
continuum optomechanics that may be accessible in future experiments.
