Blockchains are similar to tree-like data structures. In best case list like. One can argue that both lists and trees are graphs with certain restrictions. And because blockchains are directed and acyclic, they are directed acyclic graphs.

Is the above logic correct? Why / Why not?

  • 2
    While that statement it theoretically correct, it shows that the author is more interested in splitting hair with a micro-axe than in sensible discussion. From the same point, you can say that every smartphone is a computer, or that a triangle is a quadrilateral (only with two points falling onto each other), or almost every person has one leg (only that the majority of them also has another one).
    – mihi
    Dec 31, 2017 at 22:18

2 Answers 2


Here is what a blockchain looks like. The major restriction compared with a pure DAG is that a vertex (here called block) cannot have more than one parent. So, yes a blockchain is a dag with the restriction that a vertex cannot have more than one parent.

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The author's logic is correct.

To be more precise, every Blockchain is a DAG, but not every DAG is a Blockchain. This is because a Blockchain is a very specific type of DAG, one could say it's simply a "one-dimensional" DAG.

However, it is important to keep in mind that although every Blockchain is a DAG, they are generally very very different beasts.

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