Parliamentarian centralization
In any parliamentary system, the people are in possession of the political power during the election. They can, at that point, vote who will be in possession of the political power for a decided period of time. However, more and more it is so that during that decided period of governance, the people have very little to do with the political power, that becomes more and more distant from the people. The process of legislation is is not open to the people to see, not to mention affect. In fact, the system is highly bureaucratic and hierarchic. Any bureaucratic system can be described as a centralized hierarchical topologies, like star and tree.
This topology illustrates in a simplified fashion any hierarchically organized society. Bureaucracy consists of such networks. Note, that the ties are not equal, because the structure is directed. [picture: Vladis Krebs, orgnet.com]
Obviously the structure gets more complicated when going lower in bureaucracy and the bureaucracies, in democracy as well, are finally built of complex networks. However, when looking at the power hierarchy and the layers of political power, the democratic bureaucracy forms a group of hierarchical star-, tree- and bus-topologies.
More explanations and illustrations of different network topologies.