Install the virtuoso database and find that it already has 6 graphs. What are they for?

See the picture below

I tested deleting them, but when I restarted the database, three graphs were generated.
I want to know what it does.
I hope I can get your explanation! :grinning:

That is because they are system graphs that should not be deleted and hence get recreated on restart …

Thank you very much. I’m going to keep them