
The blockchain is essentially a linked list - tzakrajs
https://www.quora.com/Is-a-blockchain-essentially-a-linked-list?share=1
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QML
A better analogous structure would be the structure used in Git.

The only major difference is that Git is a DAG while a blockchain is
restricted to being a tree.

What do they have in common?

A block is a commit, containing a metadata and a hash pointing to the
preceding commit.

A Merkle tree is a tree, though restricted to having only two children; trees
in Git also contain the hashes of its children.

A transaction is a blob, the new file to be included in the next commit.

And if I recall correctly, the Git protocol was devised against a similar
issue of centralization - SVNs. If the SVN could not be reached, then you were
not able to access your repository. Since there was only one ledger, it meant
a single point of failure.

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natecavanaugh
Thank you for this. For the longest time, I actually thought the blockchain
was powered by git, or at least the DAG and associated tech concepts. But I
assumed that because it's not too far off, but it is a critical difference.

Out of curiosity, I wonder if there's a reason why it's not just built on top
of git? Is there an inherent incompatibility between the two, or some sort of
benefit to forgoing using existing tech?

~~~
QML
While similar in structure, they have different objectives: Git is for version
control of files; blockchain is for maintaining balances.

In addition, the protocol of blockchain is way more complex than the one for
Git; you have concepts like proof of work and economic problems like double
spend that have to be dealt with.

~~~
natecavanaugh
Thank you again. I forgot about the priorities, especially with how the
financial industry has a lot of different needs, such as transactional
reliability, whereas there are parts of git that are very fuzzy in different
areas because file comparison isn't as binary as a financial transaction or
have as many repercussions if off slightly.

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niyazpk
The first answer in that page (right now), is terribly misleading.

>> "As the image shows, all the nodes are connected to each other."

He is confused between a block-chain and the computing nodes in a network.

~~~
valuearb
Guess what? The answer is gone now!

I did not know that Quora did or allowed that. Did the writer remove it? Did
it get down voted to oblivion (unlikely, had positive up votes yesterday)?
Seems un-transparent.

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valuearb
Singley or doubley linked list?

Edit: Just kidding, obviously singley.

I am not a blockchain expert but don't agree with the "not at all" answer. The
illustration seems misleading, the nodes have nothing to do with the data
structure, AFAIK blocks are only linked to previous block.

I've always understood it as essentially a singly linked list where no list
node can be removed without invalidating the entire list.

Am I wrong?

~~~
lgas
You are correct. The answer on Quora is confused/misleading.

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valuearb
And gone now.

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zmonx
This title is misleading: This was formulated as a _question_ that was put
forward (verbatim text: "Is a blockchain essentially a linked list?"), and the
current answers are already now diverging between "Not at all!" and "Yes, ...
blockchain is similar to a linked list ...".

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rurban
Nope, it's a limited grow-only stack. Linked lists are unlimited, and you can
insert and delete everywhere. A blockchain not, you can only add to the top,
with deletion forbidden.

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fred_is_fred
Somewhere in a small SV office: "Reverse bitcoin on this white board"

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raverbashing
"And​Hell is just a sauna"

Over simplifications that gloss over important details

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Crontab
Is crypto-currency considered to be the most innovative use of blockchains? Is
there anything that currently doesn't use blockchains that could see a benefit
from doing so?

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adventured
Food security / safety is a trillion dollar business. There are several early
stage efforts to apply blockchain to that problem. As a segment it's almost
entirely backwards technologically (the best innovation consumers have seen on
that front in 20 years, has been laughably flawed use-by dates).

Fighting imposter products may have extremely valuable applications for
blockchain, for example knock-off Gucci bags etc. It'll take years before
authoritative systems emerge that dominate that product validation space, but
it's probably inevitable that they will.

~~~
krrrh
> Fighting imposter products may have extremely valuable applications for
> blockchain, for example knock-off Gucci bags

This example always gets brought up but Gucci bags already come with serial
numbers and receipts that you can use for lookups and registration with Gucci.
Presumably Gucci is using a database to store this information. What benefit
would consumers realize if Gucci changed out their database for one that was
immutable? Is there really any significant number of Gucci consumers who don’t
trust the company to maintain the integrity of the product database they
currently use? The interests of the company and their customers seem pretty
aligned. Perhaps there would be some benefit to having the full sales database
easily and instantly accessible by anyone in the world? But absent any demand
from consumers for them to go farther than they already have that would seem
to be outweighed by Gucci’s desire to not reveal _all_ of their sales data to
competitors (or GDPR-busting private information for that matter).

If they did want to give up such detailed information then why not just
provide weekly sql dumps on the web and avoid the consultant fees and expense
of maintaining a more inefficient database? Perhaps they could also make
customers sign a contract that prevents hem from engageing in private sales
without registering the sale with GucciCentral. The fact they have never taken
a simple steps like these to dispell any trust issues between them and their
customers tells me that there may not be many that their current systems don’t
already address adequately.

Please tell me if I’m missing something. This one has puzzled me for years.

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eyer2016
Linked list is just a digital append only ledger

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ralusek
Linked lists can prepend, append, and have items inserted or removed anywhere,
and are explicitly built around references to other nodes.

They're neither append-only, nor are they ledgers (which are basically just
logs, nowhere in the definition of which is there an implied reference to any
other item).

