  Graphs are commonly used in mathematics to represent some relationships
between items. However, as simple objects, they sometimes fail to capture all
relevant aspects of real-world data. To address this problem, we generalize
them and model interactions over time with multilayer structure. We build and
test several centralities to assess the importance of layers of such
structures. In order to showcase the relevance of this new model with
centralities, we give examples on two large-scale datasets of interactions,
involving individuals and flights, and show that we are able to explain subtle
behaviour patterns in both cases.
