The document discusses mobility modeling and contact graphs derived from real-world mobility traces. It finds that existing mobility models do not accurately capture the structural properties observed in traces, such as communities being connected by bridging links rather than bridging nodes. The traces show inter-community contacts occurring outside community locations. They also show synchronized social meetings of multiple nodes. The document proposes extending existing models with a social overlay to generate bridging links while maintaining other properties, better reflecting patterns in real-world mobility.