A dilatation structure is a concept in between a group and a differential
structure. In this article we study fundamental properties of dilatation
structures on metric spaces. This is a part of a series of papers which show
that such a structure allows to do analysis, in the sense of differential
calculus, on a metric space. We also describe a formal, universal calculus with
binary decorated planar trees, which underlies any dilatation structure.Comment: Will be available online at the site of the journal
http://www.jglta.astralgo.eu