Thank you for your reply. In response to your suggestions and the questions you posed:
Are you sure you did start Cassandra ("cassandra/bin/cassandra") before starting JanusGraph? - Yes, the Cassandra server is running. I am not using the Cassandra bundled with JanusGraph, but my own separate installation which was running at the time when I faced this issue.
Also check whether you did not mix up the graph1 and graph1_config graph.graphname values - I double-checked, and the values for the graph name that I am using are correct.
I guess you found out to do (before running bin/janusgraph-server.sh):
export JANUSGRAPH_YAML=conf/gremlin-server/gremlin-server-configuration.yaml - I am running the server using the command - gremlin-server.bat conf/gremlin-server/gremlin-server-configuration.yaml instead of storing the yaml file in an environment variable.
Apart from the above, I also ran the same commands as mentioned in my question on a 0.3.1 JanusGraph server and it worked:
Creating the graph:
Accessing the graph through the implicit variables:
The same steps give the issue posed in the question when run using JanusGraph 0.6.0: