Undoubtedly, blockchain technology has emerged as one of the most fascinating advancements in recent decades. Its rapid development has attracted a diverse range of experts from various fields. Over the past five years, numerous blockchains have been launched, hosting a multitude of applications with varying objectives. However, a key limitation of blockchain-based services and applications is their isolation within their respective host blockchains, preventing them from recording or accessing data from other blockchains. This limitation has spurred developers to explore solutions for connecting different blockchains without relying on centralized intermediaries. This new wave of projects, officially called Layer 3 projects (L3) initiatives, has introduced innovative concepts like cross-chain transactions, multi-chain frameworks, hyper-chains, and more. This study provides an overview of these significant concepts and L3 projects while categorizing them into interoperability and scalability solutions. We then discuss opportunities, challenges, and future horizons of L3 solutions and present a SWOT (Strengths–Weaknesses–Opportunities–Threats) analysis of the two groups of L3 solutions and all other proposals. As an important part, we introduce the concept of Universal decentralized finance (DeFi) as one the most exciting applications of L3s which decreases transaction costs, enhances the security of crowdfunding, and provides many improvements in distributed lending-borrowing processes. The final part of this study maps the blockchain’s triangle problem on L3s and identifies current challenges from the L3’s perspective. Ultimately, the future directions of L3 for both academic and industry sectors are discussed.

中文翻译：

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第三层区块链正在迅速发展：应对最先进的范式和未来视野


毫无疑问，区块链技术已成为近几十年来最迷人的进步之一。它的快速发展吸引了来自各个领域的各种专家。在过去的五年中，已经推出了许多区块链，托管了具有不同目标的大量应用程序。然而，基于区块链的服务和应用程序的一个关键限制是它们在各自的主机区块链中的隔离性，从而阻止它们记录或访问来自其他区块链的数据。这种限制促使开发人员探索在不依赖中心化中介的情况下连接不同区块链的解决方案。这波新项目，正式名称为第 3 层项目 （L3） 计划，引入了跨链交易、多链框架、超链等创新概念。本研究概述了这些重要概念和 L3 项目，同时将它们分为互操作性和可扩展性解决方案。然后，我们讨论了 L3 解决方案的机遇、挑战和未来视野，并提出了对两组 L3 解决方案和所有其他提案的 SWOT（优势-劣势-机遇-威胁）分析。作为重要部分，我们引入了通用去中心化金融 （DeFi） 的概念，作为 L3 最令人兴奋的应用之一，它降低了交易成本，增强了众筹的安全性，并在分布式借贷流程中提供了许多改进。本研究的最后一部分描绘了区块链在 L3 上的三角形问题，并从 L3 的角度确定了当前的挑战。最后，讨论了 L3 在学术和工业领域的未来方向。