NewGraphSessionFactory constructs a new Factory which can then be used to start a new session.

NewRoutingGraph constructs a session that which does not first start a read-only transaction and so each call on the routing.Graph will create a new transaction.

Factory implements the routing.GraphSessionFactory and can be used to start a session with a ReadOnlyGraph.

ReadOnlyGraph is a graph extended with a call to create a new read-only transaction that can then be used to make further queries to the graph.