The theory of scale relativity is an attempt at developing the consequences
of giving up the implicit hypothesis of space-time differentiability. One
of these consequences is that space-time becomes fractal, i.e., explicitly
resolution-dependent. The principle of relativity is extended in order to b
e also valid for scale transformations of space-time resolutions. In the pr
esent contribution, we mainly focus on the general structure of the theory
and on its possible future goals. This description is completed by a develo
pment of three specific points: (i) a new demonstration of the Schrodinger
equation in which all terms are kept; (ii) a method of entropy maximization
allowing one to unveil the fractal geometry from the quantum behavior. (ii
) a discussion of the metric forms in scale-relativity. (C) 1999 Elsevier S
cience Ltd. All rights reserved.