Curtiss explained they serve a similar role, but these nodes have a numerical structure to them connecting them to the semantics of the Social Graph.

Curtiss explained they serve a similar role, but these nodes have a numerical structure to them connecting them to the semantics of the Social Graph.

Facebook reaches Social Graph database benchmark: Facebook engineers discuss the development processes behind LinkBench, and how it’s being used at the world's largest social network today.

Direct Acyclic Graph or DAG may be it. What is DAG? DAG is a directed graph data structure that uses a topological ordering. The sequence can only go from earlier to later.