Polkadot is a heterogeneous multi-chain system developed based on the Substrate blockchain development framework. Substrate provides the necessary basic functional modules for the development of the blockchain. Developers can use Substrate to build parallel chains for specific businesses.
As a relay chain, Polkadot does not support smart contracts itself, but Substrate provides a solution for adding smart contract functions to parachains. Its contract module supports Wasm smart contracts.
Smart contract language ink!
The smart contract platform in the Polkadot ecosystem is dominated by Wasm virtual machines. From EVM to WebAssembly is the development trend of smart contract virtual machines. ETH 2.0 will also support Wasm virtual machines.
ink! is an embedded domain specific language (eDSL). It is a blockchain developed based on the Substrate blockchain development framework and provides a solution for writing Wasm smart contracts. ink! is built on the Rust language and follows the rules and grammar of the Rust language. It is designed to be friendly, concise and efficient.
The ink! language is composed of three abstract layers. The Core layer contains the core functions for implementing smart contracts. The Lang layer is based on the Core and Model layers. Most developers can write smart contract codes only by using the Lang layer.
Smart contract vs Runtime module
There are two different ways to build decentralized applications using Substrate: Substrate Runtime module and Substrate smart contract.
Runtime module
The purpose of the development based on the Runtime module is to generate efficient and fast nodes. It provides a low-level access interface to the entire block chain, which can completely control the low-level logic of the block chain, and can access any storage item in all modules, Make modifications and control.
However, the Runtime module has a high threshold for developers, and low-level developers may build a blockchain with incorrect logic or poor error handling. At the same time, it does not provide transaction restoration protection, nor does it introduce a charging system to the calculation of node operations. When developing the Runtime module, it is necessary to correctly evaluate the various parts of the Runtime logic and calculate the cost to avoid abuse by saboteurs to damage the entire blockchain network.
Smart contract
Substrate smart contracts allow users to add business logic to the core logic of the blockchain, while establishing a protection mechanism against saboteurs.
Smart contracts are inherently safer for the blockchain, because smart contracts cannot directly modify the storage state of the blockchain or other smart contracts. Its ability is limited to modifying its own state and making external calls to other smart contracts or Runtime functions. The calculation and storage state during the execution of the smart contract will be charged for mandatory fees, which ensures that the blockchain resources will not be abused and stored infinitely. When the execution of the smart contract fails due to various factors, the smart contract will not update the status and the transaction will be rolled back. Of course, these management overheads will reduce the efficiency of smart contract execution and increase operating costs.
Coinversation choice
Both the Substrate Runtime module and the Substrate smart contract are problem-solving tools. As for which tool to choose to solve the problem, it depends on the needs of the problem itself and the cost of development, deployment, and maintenance.
Coinversation Protocol is a synthetic asset issuance protocol and contract trading platform. The main functional modules of the entire system include: casting synthetic assets with mortgages, decentralized contract exchanges, mortgage pools, fee pools, oracles, and liquidity mining. Among them, Coinpro.MintC (the minting center for minting and destroying cUSD) and Coinpro.Exchange (decentralized exchange for trading synthetic assets) are the core products of the system. Considering that the core product needs a strict resource control mechanism and a protection mechanism for transaction rollbacks, it was decided to adopt the Substrate smart contract method for development.