In keeping with the general aim of the "D.M.V.-Seminar" series, this
book is princi- pally a report on a group of lectures held at Blaubeuren
by Professors H. J. Baues, S. Halperin and J.-M. Lemaire, from October
30 to November 7, 1988. These lec- tures were devoted to providing an
introduction to the theory of models in algebraic homotopy. The three
lecturers acted in concert to produce a coherent exposition of the
theory. Commencing from a common starting point, each of them then
proceeded naturally to his own subject of research. The reader who is
already familiar with their scientific work will certainly give the
lecturers their due. Having been asked by the speakers to take on the
responsibility of writing down the notes, it seemed to me that the
material elucidated in the short span of fifteen hours was too dense to
appear, unedited, in book form. Some amplification was necessary. Of
course I submitted to them the final version of this book, which
received their approval. I thank them for this token of confidence. I am
also grateful to all three for their help and advice in writing this
book. I am particularly indebted to J.-M. Lemaire who was indeed very
often consulted. For basic notions (in particular those concerning
homotopy groups, CW- complexes, (co)homology and homological algebra)
the reader is advised to refer to the fundamental books written by E. H.
Spanier [47], R. M. Switzer [49] and G. Whitehead [52].