Thread by @angelokappos

🧵Thread #smartcontracts on Cardano.
0/ EUTXO model extends - the basic UTXO model in such a way as to support more expressive state machines without switching to an account-based model. 2 pieces of additional functionality from the UTXO model:
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#CardanoADA

1/ - abiility to maintain the machine state,
- contract continuity, same contract code is used along the entire sequence of transactions.
- introduces three new primitives for smart contracts: The datum, the redeemer, and the validator.

2/- The only state that a smart contract can depend on is those pieces of state included as inputs, and the only state a smart contract can produce is those declared as outputs of the transaction.

3/- Transactions in Cardano are partially ordered by their dependencies, and a stake pool operator reordering things has no impact on the outcome, so MEV disappears.

4/Every Cardano transaction is deterministic:
-The user constructs, declares, and signs off on the new state of the world.
-The only way to change state is by spending UTXOs, and a given UTXO can only be spent once, so you are guarded from the state changing out from under you.

5/Ethereum and its SC language, are powerful enough to implement state machines, due to their native support for global contract instances and state. This approach has some major downsides, notably that contract state is global, and must be kept indefinitely by all core nodes.

6/ In the EUTXO model, contract state is localised to where it is used, and it is the responsibility of clients to manage it.

7/ Does Cardano have concurrency issue?
Not at all, it just have concurrency, but for sure developers and teams have got now to design a concurrent system. you can have as minimal state as you want, plus you've got finality.

8/ A powerful feature of the EUTXO model is that the fees required for a valid transaction can be predicted precisely prior to posting it. This is a unique feature not found in account-based models. In eUTXO, your fees is collected only if your transaction succeeds.

9/ Cardano only supports one transaction per block?
DApps built on Cardano are not limited to one transaction per block. In fact, the block budget (that is the maximum number of transactions it can hold) allows the execution of hundreds of simple transactions and several scripts

Check for more info here iohk.io/en/blog/posts/…

10/Contentions Issues on Cardano?
The eUTXO model allows spending a transaction output only once. Given that users can face contention issues trying to access the same UTXO, it is important to use many different UTXOs.

11/ Instead, it is accurate to say that Cardano allows a given transaction output to be spent a single time, by a single transaction, so protocols that give multiple people access to the same UTXO might face contention issues

11/ Only one user can interact with a smart contract at a time?
The point of contention is around the UTXO, but many UTXOs may be governed by the same smart contract.

12/This fundamentally comes down to the shift in thinking from Ethereum, where you call into a smart contract to make it do something, and Cardano where you lock outputs with a contract, which determine when they can later be spent.

@sapiopool @IOHK_Charles @singularity_net @InputOutputHK #alonzo #hardfork