[nootropicat]

>Data records, once written, are never updated or deleted?

>Blockchains do not allow for modification of historical data. Consider a database.

If that was true it wouldn't even be possible to send any tokens. Log of all past actions can't be deleted or updated, which is a quite different thing.

[village-idiot]

The log entries in a blockchain are supposed to be immutable. You can add new entries, but not change old ones.

[nootropicat]

It depends on how you define what a 'data record' is. State of a specific address can be changed and deleted if the contract is designed to allow it. It's directly equivalent to a normal database that keeps logs of all historical commands entered.

[decentralised]

We often talk about "blockchain as a database" but don't clarify what type of data we are discussing.

In second generation blockchains like Ethereum there's a difference between world state and ledger data. Only the Ledger data (record of state transitions) is immutable by design.

[browsercoin]

so what's wrong with Datomic? why do people insist on using blockchain?

[quellobiondo]

The point is on the ownership of the database and the trust among participants. In Datomic there is a single owner that has full control on the data (probably you, or a company that you fully trust). In the blockchain use-cases there are multiple parties that depend on the data, and no one of them is trusted enough to have full control on the database. (trust-less scenarios) Apart from Bitcoin[0] check out the original trustless timestamping service proposal [1].

[0] https://bitcoin.org/bitcoin.pdf [1] H. Massias, X.S. Avila, and J.-J. Quisquater, "Design of a secure timestamping service with minimal trust requirements," In 20th Symposium on Information Theory in the Benelux, May 1999.

[browsercoin]

In Datomic, you are responsible for the contents on it, but this is the exactly the same for people writing to the blockchain. The notion that by organizing a group of profit motivated to validate transactions is really the same thing as a centralized organization. Look at the Chinese bitcoin miners. How many times have we forked? Now the forked bitcoin is forking!

Say you took out a mortgage on an open ledger (a PoW based blockchain ledger), BYOB. What happens when you get scammed? How do you reverse the transaction? What legal enforcement is there? Remember, you've said it yourself, the blockchain's supposed value comes from that nobody has full control of the database, but this is flawed thinking-the absence of authority does not make a ledger more trustable just because it's not in the control of anyone, which is false, bitcoin being a clear example of centralized ownership, or a perfect model of "rich miners getting richer".

Trust is not a simple matter of storing information, it's much more than that. It's based on human to human level trust, which blockchain industry has pretty much failed spectacularly with the vast majority of ICO pump-dump schemes.

[dustingetz]

CDIXON: Complement effects are one of the main reasons that technology adoption is non-linear. There are other reasons, including network effects, viral product features, and plain old faddishness.

http://cdixon.org/2009/09/10/non-linearity-of-technology-ado...

Blockchain is 3 for 3!

[village-idiot]

To be fair, you can modify datomic, there’s a mutable delete operation so that you can comply with legal requirements to delete data.

[moocowtruck]

can't you technically modify block chain in the same way, rollback and fork or something? i feel like this was done for bitcoin at one point

[browsercoin]

yes. but obviously common sense goes out the window as soon as blockchain and crypto comes into play.