A wide variety of recent applications model their data in graphs/networks such as social networks, web graphs, and protein-protein interaction networks. Efcient processing for large graph data poses new challenges for almost all components of state-of-the-art data management systems. To list a few examples: (i) graph data are complex structures and cannot be efciently stored as relational tables; (ii) the access patterns of large graph processing are complex, which results in inefcient disk accesses or network communications; and (iii) last but not least, to tackle scalability issues, graph processing must be efciently distributed in a networked environment.