Exactly. Is "blockchain" just the data structure, or is it the data structure + the protocol for communication + the software to validate it? Another example

Exactly. Is "blockchain" just the data structure, or is it the data structure + the protocol for communication + the software to validate it? Another example might be bit torrent. I personally wouldn't classify bit torrent as just the data structure. I would say its the data structure, the protocol and the end clients. However if someone used these technologies to create a different format and a different protocol, I wouldn't think of it as bit torrent.