Willow addresses data by name, so a name can get new contents or none; the hash is inside the record, not the address.

It is the root of overwriting and deletion, and the main difference from content-addressed systems.

Many peer to peer systems find data by its hash. Change one byte, and it is a different thing with a different address.

Willow names data instead. Like a shelf label in a library. The label stays. The book on it can change.

Put a new book on the shelf, and the old one is gone. Same name, new contents.

Put an empty book there, and the old one is gone. That is deletion.

The hash is still there, inside the record, to check the contents. But the address is the name.

Check yourself. Where does the hash of the contents live, and what is the address?