  Techniques for the construction of dynamical Galaxy models should be
considered essential infrastructure that should be put in place before GAIA
flies. Three possible modelling techniques are discussed. Although one of these
seems to have significantly more potential than the other two, at this stage
work should be done on all three.
  A major effort is needed to decide how to make a model consistent with a
catalogue such as that which GAIA will produce. Given the complexity of the
problem, it is argued that a hierarchy of models should be constructed, of ever
increasing complexity and quality of fit to the data. The potential that
resonances and tidal streams have to indicate how a model should be refined is
briefly discussed.
