What is the difference between graph-based databases and object-oriented databases?

Question

What is the difference between graph-based databases (http://neo4j.org/) and object-oriented databases (http://www.db4o.com/)?

Answer 1

The difference at low-level is not so huge. Both manage relationships as direct links without costly joins. Furthermore both have a way to traverse relationships with the Query language, but the graph database has operators to go recursively at Nth level.

But the biggest difference is in the domain: in a Graph databases all is based on the 2 types: vertexes and edges, even if usually you can define your own types as a sort of subtypes of Vertex or Edge.

In the ODBMS you have no Vertex and Edge concepts, unless you write your own.