  The Geometry of Interaction purpose is to give a semantic of proofs or
programs accounting for their dynamics. The initial presentation, translated as
an algebraic weighting of paths in proofnets, led to a better characterization
of the lambda-calculus optimal reduction. Recently Ehrhard and Regnier have
introduced an extension of the Multiplicative Exponential fragment of Linear
Logic (MELL) that is able to express non-deterministic behaviour of programs
and a proofnet-like calculus: Differential Interaction Nets. This paper
constructs a proper Geometry of Interaction (GoI) for this extension. We
consider it both as an algebraic theory and as a concrete reversible
computation. We draw links between this GoI and the one of MELL. As a
by-product we give for the first time an equational theory suitable for the GoI
of the Multiplicative Additive fragment of Linear Logic.
