Blockchain-based smart contracts are known as “Blockchain 2.0”, which not only have the general characteristics of traditional blockchains, such as decentralization, de-trust, traceability, tamper-resistant, etc., but also have programmability and certain autonomy. So they have attracted the attention of government departments, financial institutions, science-and-technology enterprises. However, although smart contracts have shown a development trend driven by technology and industry innovation, relevant academic research is seriously lagging behind and needs to be followed up. To this end, this thesis takes“the standardization of smart contracts — the automation of smart contracts — the intelligence of smart contracts”as the main line of logic, and systematically studies the theoretical methods and applications of smart contracts, in order to standardize their academic connotations, guide their industrial practices, and inspire their future developments. The main work and contributions of the thesis are as follows:
- In order to implement the“standardization”of smart contracts, a six-layer basic architecture model of blockchain-based smart contracts is first proposed. The definition of smart contracts is given, and combined with the current mainstream development platforms, the general operating mechanism of smart contracts is proposed. Then, combined with the design process and components, the whole life cycle of smart contracts is divided into six stages: negotiation, development, deployment, maintenance, learning and self-destruction. On that basis, a basic architecture model of smart contracts which employs a six-layer framework, i.e. infrastructures layer, contracts layer, operations layer, intelligence layer, manifestations layer, and applications layer is proposed, and the components of each layer are described in detail. The proposed model not only covers the key technologies in the whole life cycle of smart contracts, but also reflects their future research directions and development trends.
- On the basis of“standardization”, and combined with the prediction markets, a typical case realization of smart contracts is given. Prediction markets have good predictive ability, but for a long time they have also faced problems such as easy market manipulation and poor security. Considering that the prediction market is a market in which buyers and sellers trade the forecast of future events in the form of contracts, we think that it is well suited to be combined with the blockchain, especially by means of smart contracts. So we propose a prediction market contracts design and algorithms implementation scheme based on smart contracts, and deploy the prediction market on an internal private blockchain of an enterprise. The application example shows that the smart contracts-based prediction market can not only achieve its forecasting function, but also overcome the problems of easy market manipulation and poor security in the previous prediction markets.
- In order to realize the “automation” of smart contracts, we take the domain knowledge graphs construction as the research and application background, and propose a novel decentralized knowledge graphs construction method based on smart contracts, and apply the constructed knowledge graph to the deep recommender system. Aiming at the problems of traditional construction approaches of knowledge graphs, such as laborious and time-consuming, vulnerable to manipulation, and the data is monopolized by the centralized institutions, we propose that it can be realized through crowdsourcing-enabled group intelligence, and blockchain-powered smart contracts are used to execute the business logics of crowdsourcing, thus making the construction process decentralized, transparent, auditable and tamper-resistant. The crowdsourcing voting and its smart contracts implementation scheme are detailed. Then, a deep recommender system consisting of on-chain and off-chain part is proposed, which is designed to complete the candidates recommendation of the work task and help the enterprise to realize the business process automation. The overall architecture of the recommender system, the knowledge graph embedding methods, and the network model of the off-chain deep recommender system are introduced. Finally, the effectiveness of the system is validated by case study.
- In view of the fact that the current smart contracts are neither “smart” nor“contract”, the concept of smart contracts-oriented “Intelligent ware” is proposed.“Intelligent ware”is a pluggable, autonomous blockchain system core function module that combines artificial intelligence algorithms. It can automatically select and configure the optimal wares combination for specific scenarios and computational tasks. In essence, “Intelligent ware”comes down in one continuous line with the development history of artificial intelligence and the evolution of programming languages, so it is expected to be an effective form and possible implementation path for smart contracts to move toward “intelligence”. A smart Oracle implementation scheme based on ASKE (Application Specific Knowledge Engines) is proposed as a preliminary implementation of the proposed “Intelligent ware”. Finally, the future applications and manifestations of smart contracts/intelligent wares — the Decentralized Autonomous Organization (DAO) is systematically elucidated, and a reference model for DAO which employs a five-layer architecture is proposed.