Is RDF a graph?

A graph consists of a set of vertices (nodes, points) and a set of edges (arcs, lines) between nodes. The common definition is  G = (V, E)  where V representes the set of vertices and E represents the edges between two vertices.

Commercially, there are two specific types of graph data models: Property Graph and RDF Graph.  A property graph is a graph where key-value pairs can be associated to vertices and edges. An RDF graph is a represented as a set of triples: subject, predicate, object where the subject and object are vertices and a predicate is an edge.

However, it seems that Jim Webber, Neo4J’s Chief Scientist does not acknowledge that RDF graphs are graphs:

My response and Jim’s follow up response:

and my response:

It is still unclear to me why Jim Webber believes RDF graphs are not graphs?

Jim, I’m in London this week. I would love to meetup, have a pint and chat about graphs!