The next-generation blockchain ecosystem is expected to integrate both homogeneous and heterogeneous distributed ledgers. These systems require operations across multiple blockchains to enrich advanced functionalities for future applications. However, the development of blockchain interoperability involves much more complexity regarding the variety of underlying architectures. Guaranteeing the properties of ACID (Atomicity, Consistency, Isolation, Durability) across diverse blockchain systems remains challenging. To clear the fog, this article accordingly provides a comprehensive review of the current progress of blockchain interoperability. We explore the general principles and procedures for interoperable blockchain systems to highlight their design commons. Then, we survey practical instances and compare state-of-the-art systems to present their unique features between distinct solutions. Finally, we discuss critical challenges and point out potential research directions. We believe our work can provide an intuitive guideline for newcomers and also promote rapid development in terms of blockchain interoperability.

下一代区块链生态系统预计将集成同构和异构分布式账本。这些系统需要跨多个区块链进行操作，以丰富未来应用的高级功能。然而，区块链互操作性的开发涉及各种底层架构的复杂性。保证不同区块链系统的 ACID（原子性、一致性、隔离性、持久性）属性仍然具有挑战性。为了拨开迷雾，本文对区块链互操作性的当前进展进行了全面回顾。我们探索可互操作的区块链系统的一般原则和程序，以突出其设计的共同点。然后，我们调查实际实例并比较最先进的系统，以展示不同解决方案之间的独特功能。最后，我们讨论了关键挑战并指出了潜在的研究方向。我们相信我们的工作可以为新人提供直观的指导，并促进区块链互操作性方面的快速发展。