Finally, I found somebody clarifying the very concept of embodiment. It's amazing how many papers deal with this concept without giving a proper definition. The definition is rather robot-design oriented (than an interaction design twist) but it still of interest.
Despite the fact that exploiting embodiment offers real opportunities to those who would design and build robots, the term is typically used without being directly defined. A significant initial assumption in almost all cases is that to be 'embodied' is 'to have a physical body.(...) A system X is embodied in an environment E if perturbatory channels exist between the two. That is, X is embodied in E if for every time t at which both X and E exist, some subset of E's possible states with respect to X have the capacity to perturb X's state, and some subset of X's possible states with respect to E have the capacity to perturb E's state.