The oft-cited words registry, book, and journal are abstract instantiations of the term “DLT-table”. A DLT table is a technical term that defines a two-dimensional array data structure created long before bitcoin.
The differences can best be seen in examples. Current DLT examples include Ripple, because just two weeks ago Bank of America filed a patent application for a settlement system based on Ripple distributed ledger technology. Ripple’s developments are excellent for banks and really find practical application, so their technology is worthy to act as a representative of DLT.
Classic examples of blockchain are bitcoin and etherium, so they will be representatives from the blockchain family.
Substitution of concepts
The illustration shows that distributed ledgers are a basic distributed database technology, while blockchain is just a type of DLT. The main difference is one important aspect: decentralization.
In public blockchain, anyone can become a miner or set up a node to directly participate in data validation, while DLT tables can be private. Blockchain is necessarily open for everyone to use and manage, while DLT structures are necessarily distributed, but not necessarily decentralized.
The difference between decentralized and distributed is best explained in S. Raval’s book “Decentralized Applications. Blockchain technology in action”, but if you don’t have time to read it, this illustration from the book will help guide you.
The notion of “private blockchain” is even more misleading. Such a phrase should not exist at all, and its creation is the fault of marketers, who in 2017-2018 to promote products based on private distributed registries began to add the hype word “blockchain” to them en masse. As a result, the concept of blockchain has morphed into “public blockchain” to avoid confusing God’s gift with the egg.
“In the corporate space, people apply the concept of ‘private blockchains,’ even though it is fundamentally wrong from a technical standpoint. Such products are not blockchains at all; rather, they can be called an advanced database management system.”
Chen does give credit to private blockchains in terms of technology development, though: “The performance gains over classic blockchain are huge. I would even give these innovations a score of 9 to 10, whereas the public blockchains of Bitcoin and Ethereum can be given a score of 0 to 1.
Unfortunately, the technologies on which Bitcoin and Ethereum are based have proven inconvenient for mass adoption, while private distributed registries are better suited for practical implementation in many aspects. The proof is in the list of the richest corporations investing in blockchain. Nine out of ten companies use DLT-based products.
In a distributed DLT ledger, the number of people who can become a node, use and access it is limited. Management decisions are left to a single company or group of companies, as in Facebook’s Libra blockchain. Compared to Bitcoin and Ethereum, the Ripple DLT serves the interests of a concentrated group of commercial corporations, in this case banks. And banks have absolutely no need for a public blockchain, if only for reasons of privacy of their customers’ data.
As for the timestamp of adding data, it can be in a public blockchain as well as in a regular DLT table, so transaction timestamps cannot be attributed to the differences. As an example, take Corda R3, a distributed DLT that has a consensus algorithm and timestamps, but no blockchain.
So, the main difference between the general concept of DLT and blockchain is decentralization, which is optional in DLT but mandatory in public blockchain.