abstract: The notion of interval identification systems (IIS) is a natural generalization of interval exchange transformations and interval translation mappings.
We are interested in particular case of such systems - symmetric IIS of order 3 due to some interesting application to 3-dimensional topology.
We define a Rauzy induction for these systems and prove a renormalization theorem which provides us with a Markov map and a fractal in original parameter space. We are interested in ergodic properties of corresponding dynamical system and in Lebesgue measure of this fractal.