The observation that many models are built but few are used has almost
become a commonplace in the management science and operations research
literature. Nevertheless, the statement remains to a large extent true
today, also and perhaps even more so where marketing models are
concerned. This led Philippe Naert, now about four years ago, to write a
concept text of a few hundred pages on the subject of how to build
imple- men table marketing models, that is, models that can and will be
used. One of the readers of that early manuscript was Peter Leefiang. He
made suggestions leading to a more consistent ordering of the material
and pro- posed the addition of some topics and the expansion of others
to make the book more self-contained. This resulted in a co-authorship
and a revised version, which was written by Peter Leefiang and consisted
of a reshuffling and an expansion of the original material by about
fifty per cent. Several meetings between the co-authors produced further
refinements in the text and the sequence of chapters and sections, after
which Philippe Naert again totally reworked the whole text. This led to
a new expansion, again by fifty per cent, of the second iteration. The
third iteration also required the inclusion of a great deal of new
literature indicating that the field is making fast progress and that
implementation has become a major concern to marketing model builders.