Categorification and group extensions (Q1597417)

In recent times it has become evident that in many contexts where we are tempted to use sets or groups, it is actually more natural to use a richer sort of structure, namely a kind of `higher-dimensional' set or group. The categorification can be viewed as a bridge allowing to transport constructions from the category of sets into categorical terms. This paper is an example of it. More concretely, the author applies a categorification of group extensions to nonabelian group cohomology. He gives an interpretation of the classical Schreier theory in categorical terms.