Underestimate blockchain at your peril

> categorizing blockchain as 'just another useful data structure' appears to me to miss the underlying potential of this innovation

I struggle with characterising it as a data structure. Yes, it's true crypto currencies are built around a data structure. For example, at 1000' level Bitcoin's block chain is just a linked list. But not all crypto currencies use a linked list. For example IOTA uses a dag.

One thing they do have in common is they are "append only". Earlier history is immutable. And all use some technique for rendering that history immutable. But how they do it varies. Bitcoin uses proof of work, others use proof of stake, some rely on some variant of solving Byzantine generals problem I in a way I don't understand.

Another thing they have in common is the currency is built around a set of rules. Rules such as no double spends, the block must be sealed by proof of work, the owner must authorise the transfer coins in some manner. In fact there is always a lot of rules with complex interactions that are somehow self re-enforcing, meaning once the system is established it becomes very hard to break the rules - because of the rules. (Yes, that is horribly self referential. /me scratches head. Anyway, as anybody who has raised a 2yo knows, most sets of rules don't have that property. Yet bitcoin whose history is streaked with both criminals and criminal incompetence, and whose main users for a while were criminals, doesn't have a problem with any of the criminals breaking bitcoin's self imposed rules.) The thing that is unusual is the lump of appended to the data structure is in a sense self validating, meaning its possible to verify a new block adheres to _all_ the rules by looking just at the block and prior history.

I guess it may be possible to design an API that somehow encapsulates these things. But I pretty certain no single data structure could do it.