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Comment by kba | Hacker News Reader

Then there'd be a negative amount of apples. It's not impossible if you disregard context.

There is nothing new about doing things like this, OT and CRDT have existed for ages. Check out ShareDB (https://github.com/share/sharedb) or Webstrates (https://webstrates.net/) (based on ShareDB). In Webstrates, we don't have merge conflicts that need to be resolved and there are never any practical synchronization issues. The server orders the operation and if you try to delete something that's already been deleted, then we just ignore your operation.

Also quite courageous to say something is impossible when you have the code that does it right in front of you. ;-)

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I think when we say "impossible" we mean "well sure any old thing is possible but there are hard limits on what's consistent and sane."

I will go read the docs in more detail but what you've just describes sounds pretty awful. Perhaps it's more just you being glib about non-cooperative actors in an environment that expects cooperatuon, but an "available balance" abstractions are a pretty reasonable thing to ask for, if only to encode natural numbers.

I'm not one to dictate how technologies like these are to be used, but all I can say is that in the almost two years I've been working on Webstrates – a collaborative system using a very similar technology – this has not been an issue.

But surely, if you allow malicious actors to modify your document, then that's your problem right there.

It's still impossible in the general case. You merely proved him right. Limiting yourself to OTs and CRDTs is a signficant restriction.

Why is that a restriction? You can make any changes to the JSON you wish, you just have to use their API.

ShareDB looks quite interesting. We wanted similar capabilities but without a central authority, thus automerge was born.

We've been wanting to try a CRDT-based implementation with Webstrates for some time, but haven't found a suitable implementation, so this looks very promising!

Any particular reason why you choose CRDT over OT?

I'm told OT gets very complicated, and I hoped a good CRDT would be general-purpose enough to cover a variety of applications and domains. Also, I like not needing a central server to coordinate action. Would love to compare notes -- feel free to reach out to me on twitter at the same nick.

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