Is my blockchain a blockchain?

This article was originally published at https://gist.github.com/joepie91/e49d2bdc9dfec4adc9da8a8434fd029b. 

Your blockchain must have all of the following properties:

• It's a merkle tree, or a construct with equivalent properties.
• There is no single point of trust or authority; nodes are operated by different parties.
• Multiple 'forks' of the blockchain may exist - that is, nodes may disagree on what the full sequence of blocks looks like.
• In the case of such a fork, there must exist a deterministic consensus algorithm of some sort to decide what the "real" blockchain looks like (ie. which fork is "correct").
• The consensus algorithm must be executable with only the information contained in the blockchain (or its forks), and no external input (eg. no decisionmaking from a centralized 'trust node').

If your blockchain is missing any of the above properties, it is not a blockchain, it is just a ledger.