A block-tree would be append only. The blockchain is a block-tree + a canonical leaf (or a head) which is a mutable variable.<p><a href="https:&#x2F;&#x2F;medium.com&#x2F;@arthurb&#x2F;what-do-blockchains-accomplish-e9a5efa246bf" rel="nofollow">https:&#x2F;&#x2F;medium.com&#x2F;@arthurb&#x2F;what-do-blockchains-accomplish-e...</a>