I'm requesting key-value formatted data that is attached to a world portal and stored in memory for the next world to read when the player enters the portal.
This would be modifiable at runtime, and would be filterable on the receiving side.
The receiving world could have a whitelist of world id's in the scene descriptor, if they wanted to filter what worlds they allow data from.
This effectively would let you transfer data between worlds, of course this can come with limits on the amount of data that can be passed along, but it could give rise to multi-world experiences and smaller world sizes overall.