The final level to discuss is the presentation layer, which consists of the use of a website and web3 libraries in order to retrieve data from the blockchain to put on a web page, and in order to write data back to the blockchain in the form of transactions, usually using an integrated web browser blockchain wallet such as MetaMask.  The thing to realize here, is that the web site developer has complete control over how they present the data they retrieve from the blockchain to the user. They can present it as is, or they can alter some or all of it.  There is nothing about a blockchain that forces the web developer to be honest in this presentation, and I give an example in this video of how I did just that to Anthony Day in the SOULS website ( visit https://souls.fi/  for more ).

This is a digression into why the layers that I am talking about in this video series are not related to "layer 2 solutions" like Polygon and Binance Smart Chain. Instead I'm talking about layers in the same manner as the upper layers of the OSI seven layer model.  I find it odd that "layer 2" solutions use the word "layer", because they don't really sit on top of the base blockchain that they use for anchoring (i.e. the Ethereum blockchain). Instead they kind of sit beside it, with bridges in order to transfer assets from Ethereum onto these sidechains.  You see, there already was a word that worked -  sidechains. I guess it didn't pass muster with the marketing people. Or perhaps you can explain to me why we need to use the term "layer 2" instead of sidechain for things like xDai or Polygon, because it's not obvious to me.

As a developer, you have a choice as to what blockchain you use, but very little if any control over the mechanisms that power it.   It's a bit like choosing a country and a language to write your book in.  If it's a smart contract blockchain, move up a level, and you can start to exert more control - for example, you can release a centralized token on a decentralized blockchain, if you so choose. But there are still some fundamental things that you will be tied to, if you want your contract to have traction.  Similarly, as a writer you can bend the rules of grammar or coin new words, but go overboard and your audience will think you're speaking gibberish.  Then there's a third level, namely web3, which acts as a presentation layer. On this layer you can really go to town. There will be more on this in the final video in the series.

In this video, part three of the series, I talk about how smart contract blockchains such as Ethereum allow developers to play with levels of decentralization in the smart contracts they deploy.  For example, although Ethereum is "censorship resistant" due to it's blockchain consensus system, it is perfectly possible to release smart contracts that are highly centralized, under the control of one entity, and therefore vulnerable to censorship.  For example, it was revealed during the Compound bug that Tether can "freeze" transfers on certain balances in the way that traditional banks can freeze accounts.  I also talk about levels of "arbitrariness" found at the different levels in the blockchain.

Having looked at what a ledger is, and why the concept of a ledger is significant within blockchain, it's time to move up a layer and consider "ledgers within ledgers".  When a smart contract instantiates a fungible or non-fungible token, what it is doing is implementing another ledger in order to keep track of the balance or ownership of the token.  So - tokens are created by building legders within ledgers.  This video goes into what that means at greater depth.

In this video, I start with a recap of what a ledger is, in order to set the groundwork for later videos on the different levels that exist in blockchain.  This will help you to understand what is going on in cryptocurrencies and NFTs, and what parts are arbitrary, and which are fixed.  (Well, ultimately all of blockchain is arbitrary, because we invented it, but some parts are now fixed, and other parts can be "played with". But more on that later in the series...)