How to create multiple graphs with TitanDB (+Cassandra) in the same machine?
See https://github.com/thinkaurelius/titan/wiki/Using-Cassandra
scroll down to "Cassandra Specific Configuration", and
use property "storage.keyspace=" to use multiple keyspaces in cassandra.
Each keyspace will hold a graph. (default keyspace is 'titan'.

So, if you want 3 graphs, create 3 config files, with diff "storage.keyspace" property.

When you open a graph from your client using TitanFactory.open(config), use the appropriate config file.