We are happy to announce that the following paper was accepted to the 21st International Conference on Implementation and Application of Automata (CIAA 2016). Multitape Rational Expressions Akim Demaille EPITA/LRDE We introduce (weighted) rational expressions to denote series over Cartesian products of monoids. To this end, we propose the operator | to build multitape expressions such as (a⁺|x + b⁺|y)*. We define expansions, which generalize the concept of derivative of a rational expression, but relieved from the need of a free monoid. We propose an algorithm based on expansions to build multitape automata from multitape expressions.