  We present a multimodal interaction framework suitable for a human rescuer
that operates in proximity with a set of co-located drones during search
missions. This work is framed in the context of the SHERPA project whose goal
is to develop a mixed ground and aerial robotic platform to support search and
rescue activities in a real-world alpine scenario. Differently from typical
human-drone interaction settings, here the operator is not fully dedicated to
the drones, but involved in search and rescue tasks, hence only able to provide
sparse, incomplete, although high-value, instructions to the robots. This
operative scenario requires a human-interaction framework that supports
multimodal communication along with an effective and natural mixed-initiative
interaction between the human and the robots. In this work, we illustrate the
domain and the proposed multimodal interaction framework discussing the system
at work in a simulated case study.
