The study of classes of models of a finite diagram was initiated by S. Shel
ah in 1969. A diagram D is a set of types over the empty set, and the class
of models of the diagram D consists of the models of T which omit all the
types not in D. In this work, we introduce a natural dependence relation on
the subsets of the models for the N-0-stable case which share many of the
formal properties of forking. This is achieved by considering a rank for th
is framework which is bounded when the diagram D is N-0-stable. We can also
obtain pregeometries with respect to this dependence relation. The depende
nce relation is the natural one induced by the rank, and the pregeometries
exist on the set of realizations of types of minimal rank. Finally, these c
oncepts are used to generalize many of the classical results for models of
a totally transcendental first-order theory, in fact, strong analogies aris
e: models are determined by their pregeometries or their relationship with
their pregeometries; however the proofs are different, as we do not have co
mpactness. This is illustrated with positive results (categoricity) as well
as negative results (construction of nonisomorphic models). We also give a
proof of a Two Cardinal Theorem for this context. (C) 2000 Elsevier Scienc
e B.V. All rights reserved. MSC: 03C45; 03C75.