I. Introduction
Communication, be it verbal or not, is a key aspect for the success of a Human-Robot collaborative task. This becomes especially important in complex environments with a wide variety of entities: objects, places, people. Referring to a specific entity in such an environment can become challenging when one must account for the context of the task, the variety of facts that can be extracted from the situation depending on available perception modalities and the common ground between the robot and its human partners. The need to communicate on particular objects happens in many everyday tasks and it is important to endow the robot with the ability to estimate if and how referring to an object is feasible as well to assess the intelligibility of a referring expression (RE). This need is also important since deictic pointing is not always available in cooperative tasks when hands might be occupied to do something else.