Intro
Acknowledgments
Contents
Acronyms
1 An Introduction to Web3 and Metaverse
1.1 Introduction
1.2 Introduction to Web3
1.2.1 Definition of Web3
1.2.2 From Web1.0 to Web3.0
1.2.3 Technological Development Stack of Web3
1.2.4 Implication of Web3
1.3 Introduction to Metaverse
1.3.1 Definition of Metaverse
1.3.2 Three Early Stages of Metaverse
1.3.2.1 Conception Forming Period
1.3.2.2 Technique Shaping Period
1.3.2.3 Rapid Development Period
1.3.3 Key Technologies for Metaverse
1.3.4 Hierarchical Structure of Metaverse Ecosystem

1.3.5 Iconic Events of Metaverse
1.4 Fundamentals of Web3 and Metaverse
1.4.1 Blockchains
1.4.2 Smart Contracts
1.4.3 Digital Assets and Tokens
1.4.4 Typical Applications Related to Web3 and Metaverse
1.4.4.1 Games
1.4.4.2 Virtual World Metaverses
1.4.4.3 Social Network Projects
1.4.4.4 DAOs
1.4.4.5 DeFi
1.4.5 Digital Identity in Web3 and Metaverse
1.4.5.1 Introduction to Digital Identity
1.4.5.2 Taxonomy of Constructing the DID Ecosystem
1.4.5.3 Summary of DID
1.5 Brief Review of Related Works
1.6 Conclusion
References

2 How to Enrich Metaverse? Blockchains, AI, and Digital Twin
2.1 Introduction
2.2 How Blockchain and AI Enable Metaverse
2.2.1 An Open Metaverse Needs Blockchains
2.2.2 High-Performance Blockchains Are the Foundation of Future Metaverse
2.2.3 Artificial Intelligence in Metaverse
2.2.4 Representative AI Algorithms
2.2.5 Establishment of Metaverse Environment
2.2.6 Intelligence for Metaverse
2.2.6.1 Avatar and Non-player Characters
2.2.6.2 AI-Driven Activities in Metaverse
2.2.7 User-Generated Content (UGC)
2.2.8 Professional-Generated Content (PGC)

2.2.9 Artificial Intelligence-Generated Content (AIGC)
2.3 Fusing Blockchain and AI with Metaverse
2.3.1 Blockchain for AI
2.3.2 AI for Blockchain
2.4 How Digital Twin Enables Metaverse
2.4.1 Taxonomy and Characteristics of Digital Twin
2.4.2 Advantages of Digital Twin
2.4.3 Existing Applications and Expectations
2.4.4 Cutting-Edge Topics in Academia
2.4.4.1 An Overview of Related Studies
2.4.4.2 Digital Twin Edge Networks (DITENs) Toward 6G
2.4.4.3 Digital Twin as a Service
2.5 Challenges and Open Issues
2.5.1 Open Issues on Digital Economy in Metaverse

2.5.2 Artificial Intelligence Issues
2.5.3 Blockchain-Related Issues
2.5.4 Governance for Metaverse
2.5.5 Blockchain-Empowered Applications for Metaverse
2.5.6 Security and Privacy for Metaverse
2.6 Conclusion
References
3 How to Address Storage Issues for Metaverse? Blockchains and Distributed File Systems
3.1 Introduction
3.2 Preliminaries
3.2.1 Merkle Tree and Merkle DAG
3.2.2 Overview of BitTorrent
3.3 The Layered Structure of Blockchain-Based Distributed File Systems
3.3.1 Identity Layer
3.3.2 Routing Layer
3.3.3 Network Layer
3.3.4 Data Layer