foreword

The core innovation of the blockchain is that it can transfer value without trusting a third party. Therefore, for a public chain with a sufficiently high degree of decentralization, the authenticity of the information transmitted on the chain can be guaranteed. of. But there is still a problem that cannot be solved. People live in an off-chain world. Many empirical rules and conclusions are obtained by summarizing off-chain data, and writing data from off-chain to on-chain requires people to do it.