Desk
Who filed it
The desk name is the newsroom that handed the item to this host.
Copy desk
Which desk filed the item on this host.
The source card is the filing note: the desk that sent the item, and the revision clients should keep.
Item
Not the body
This route identifies the filing. The text of the item lives on its own route.
Revision
What to keep
Clients store the revision and skip a download when it has not moved.