INVITED
PAPER

Overlapping Communities
Explain Core–Periphery
Organization of Networks
The paper presents a new paradigm for uncovering the modular structure of complex networks.
By Jaewon Yang and Jure Leskovec

ABSTRACT

|

Networks provide a powerful way to study

food web networks have a single central dominant core while

complex systems of interacting objects. Detecting network

communities in protein–protein interaction (PPI) as well as

communitiesVgroups of objects that often correspond to func-

product copurchasing networks have small overlaps and form

tional modulesVis crucial to understanding social, technolog-

many local cores.

ical, and biological systems. Revealing communities allows for

| Community detection; core–periphery structure;

analysis of system properties that are invisible when consid-

KEYWORDS

ering only individual objects or the entire system, such as the identification of module boundaries and relationships or the

ground-truth communities; networks

classification of objects according to their functional roles.
However, in networks where objects can simultaneously belong to multiple modules at once, the decomposition of a network into overlapping communities remains a challenge.
Here we present a new paradigm for uncovering the modular structure of complex networks, based on a decomposition of a network into any combination of overlapping, nonoverlapping, and hierarchically organized communities. We demonstrate on a diverse set of networks coming from a wide range of domains that our approach leads to more accurate communities and improved identification of community boundaries. We also unify two fundamental organizing principles of complex networks: the modularity of communities and the commonly observed core–periphery structure. We show that dense network cores form as an