This third course of the Blockchain specialization prepares you to design and develop end-to-end decentralized applications (Dapps) – which provide anyone with access to the blockchain’s features and services. You will use Truffle IDE, smart contracts, a simple web client and a MetaMask client. You will learn about the architecture of a Dapp: the front-end client interface, backed by the blockchain and smart contracts. The course covers the basic design of a Dapp, Truffle development process and commands (init, develop, test and migrate), test-driven development of Dapp, Dapp application models and emerging standards that are essential for predictable Dapp behavior. Main concepts are delivered through videos, demos and hands-on exercises.
Application Models & Standards: Dapp Models (Part 1)
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Del curso dictado por University at Buffalo
Decentralized Applications (Dapps)
19 calificaciones
De la lección
Application Models & Standards
We will discuss Ethereum Improvement Proposal and the ERC process that are essential for keeping Ethereum blockchain updated. We will also explore the standard ERC 20 for token Dapps and ERC 721 for non-fungible tokens.
Conoce a los instructores
Bina RamamurthyTeaching Professor
Computer Science and Engineering Department
We've learned a lot about developing end to end Dapps in this course.
Have you wondered, what problems Dapps can solve?
What are some use cases?
We can find many current examples for Ethereum-based Dapps in this lec.
Our aim in this open ended module of the Dapp course is to
explore some of the models of Dapp and its ecosystem.
We hope these discussions,
will encourage you to think about new work and
possibly disruptive application and application models.
There is still work to be done for developing Dapps and also
contributing to the protocol improvements and imagining newer Dapp models.
On completion of the module,
you will be able to list the different application models of DApp and explain
Ethereum improvement proposal (EIP) and a Ethereum requests for Comments frameworks.
You will also be able to explain the importance of standards in a decentralised system
and explore two standard tokens: ERC 20 and ERC721.
We gotta stop this lesson on Dapp model with
a hierarchy diagram that gives a high level view of Various Dapp model,
starting from the genesis of Bitcoin.
In this lesson, we'll review each of these models.
We acknowledge that there are many others not included
and that this diagram is by no means complete.
We encourage you to add the Models to this diagram.
After this lesson, you will be able to list some important models of Dapp
and explain the evolution of Dapp models from cryptocurrencies to cryptoassets.
Let's explore the models one by one.
Bitcoin is the PR cryptocurrency.
Every Bitcoin was minted by the protocol,
except for the genesis transaction from satoshi to halving.
Innovation of bitcoin is the decentralized payment system that is still running,
though facing issues with scalability and price volatility.
Next, the coin and
the initial coin offering bitcoin code-base is
open source and the initial response to Bitcoin from the developer community,
with the releases of many new crypto currencies.
Then came the innovation of Etherium Smart Contract.
It helped automate the crowd funding for startups using
a wood-joint instrument called Koine and the process of initial coin offering.
This is similar to an initial public offering IPO of company stocks.
Coin ICO use a block chain to record the distribution of the coin,
receive funds, specified rules,
and to enforce any preconditions and policies.
For example a policy of some of
the Chinese ICEOs is that they would not receive funds from the USA.
That is atleast at the time of our recording.
In the Dapp hideout key,
we have included only as coined Dapps, Ethereum, and Zcash.
However, there are hundreds of ICOs and coin offerings.
It has become a popular mode for crowdfunding.
Did you know the Zcash focuses heavily on privacy and uses closed-code?
We classify any cryptocurrency that race France through ICOs in the coins Dapps.
Both Ethereum and Zcash used ICO processes for that initial funding.
That's the reason for classification of Ethereum and Zcash in this category.
The next Dapp we will look at is Tokens and initial token offering.
Sometimes tokens and coins are used synonymously.
However, we distinguish between these in our model.
Token is like a Dapp coin but,
its offering is typically associated with an asset or utility.
For example, in the highly popular cryptoKitties,
a token is used to represent the kitty or all the rules for the creation lifecycle,
breeding etc are written into the immutable Ethereum block chains Smart Contract.
At pre-determined times, a certain number of new tokens are
released and auctioned off for raising new funds.
Assets are Kittys in this case,
also appreciate or depreciate in price based on the demand.
So the tokens are non-fungible.
In other words, value for Tokens can change during its lifetime.
Auger is a prediction Dapp that depends
on the system of crowd and their reports on deputation,
offer product to predict markets.
These decentralized participants or crowd get paid in REP tokens or reputation tokens.
These tokens represent a fraction of the fees collected if the transaction gets executed,
based on the crowds reporting.
Once again there are so many token Dapps in play,
but we have covered only two.
In the hierarchy diagram,
you will also notice that both Auger and cryptoKitties
inherit from standard tokens ERC 20 and ERC 721 respectively.
More on this, in the next lesson.
Turn your attention to DAO,
a Decentralized Autonomous Organization is an early innovation in Dapp.
DAO was an investment instrument deployed as a smart contract on Ethereum block chain.
Autonomous venture capital Dapp to be exact.
The idea was to showcase an autonomous organization without
traditional corporate governance structure for
a decentralized anonymous Fund-Raising, an automatic investing.
DAO was deployed prevalently without extensive testing.
But the idea itself was well received and DAO raised funds beyond expectation.
However, a Waldner Byzantine's code was exploited by hackers.
This resulted in a digital heist of a significant portion of the collected funds.
You can read more in the ether thief,
placed in the resource section.
Actual events do indeed read like a thriller.
It is a nice plot for a movie.
The readers digest version of this.
This DAO heist and the solution to fix it,
resulted in the unexpected hard fork of Ethereum in July 2016.
This hard fork split Ethereum to ETH core as we use it now an ETC,
the Ethereum classic that still has the DAO bug in it.
In spite of all the negative publicity,
we feel that the Decentralized Autonomous Organization
is indeed an innovative Dapp If done right.
The next Dapp model is Decentralized Marketplace.
This is an easy low hanging fruit for Dapp.
They defined marketplace broadly,
it could be a Dapp for anything from selling goods to education credentialling.
Remember a market-place facilitates meetings of sellers and buyers.
You can build a marketplace platform where decentralized buyers and sellers,
those unknown to one another can meet and exchange items with
the payment and transaction recorded and
on any of the established block chain technologies,
such as Bitcoin or Ethereum.
You can always use Bitcoin as a payment system with a global marketplace you build.
Is that a sample smart contract code for supporting buying or selling?
Yes, that is an example is safe for
remote purchase smart contract in purchase.sol in the solidity documentation.
One more idea to discuss is FinTech.
FinTech short for financial technology,
has great potential for innovative Dapps.
This domain ranges from Decentralized Investment Instrument to Micropayment Channels.
Currently, a significant issue for FinTech Dapps is
the high conformation times of the transactions compared to the centralized technologies.
At the time of this recording,
Dapps cannot meet the subsecond trade confirmation times.
The decentralized systems can deliver for stock trading.
In this case scalability is a dominant issue.
Privacy is another issue to be considered in this context.
Regulation and policies of the U.S. Securities and Exchange Commission FCC and
the counterpart organization in many countries
have an effect on the FinTech Dapps and the development.
Security, privacy, safety, and proud Provins are major issues.
In fact, token, coins,
and ICO Dapps provide a backdoor entry for
many investors and financial institution into the cryptocurrency markets.
In summary, in this lesson we looked at a few of the D.F.
models, we've not covered them all,
and many in a way two models have had to be created.
After all [inaudible] b sharing apps came into existence 30 years after the advent of the Internet.
You can use the Dapp models discussed as an inspiration
and as a guideline to create a Dapp for your application domein.
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