  Complex institutions are typically characterized by meso-scale structures
which are fundamental for the successful coordination of multiple agents. Here
we introduce a framework to study the temporal dynamics of the node-community
relationship based on the concept of community alignment, a measure derived
from the modularity matrix that defines the alignment of a node with respect to
the core of its community. The framework is applied to the 16th legislature of
the Italian Parliament to study the dynamic relationship in voting behavior
between Members of the Parliament (MPs) and their political parties. As a novel
contribution, we introduce two entropy-based measures that capture politically
interesting dynamics: the group alignment entropy (over a single snapshot), and
the node alignment entropy (over multiple snapshots). We show that significant
meso-scale changes in the time-dependent network structures can be detected by
a combination of the two measures. We observe a steady growth of the group
alignment entropy after a major internal conflict in the ruling majority and a
different distribution of nodes alignment entropy after the government
transition.
