A Cross-Chain Query Language for Application-Level Interoperability Between Open and Permissionless Blockchains

TL;DR

This paper proposes a cross-chain query language to enable application-level interoperability across open and permissionless blockchains, addressing current challenges of inhomogeneous data access and feature disparities.

Contribution

It introduces a standardized syntax, data model, and processing architecture for a cross-chain query language tailored for decentralized applications.

Findings

Demonstrates language syntax and data model compatibility with major blockchains

Provides an architecture for unified data access across multiple chains

Evaluates the language's effectiveness in real-world blockchain environments

Abstract

Open and permissionless blockchains are distributed systems with thousands to tens of thousands of nodes, establishing novel platforms for decentralized applications. When realizing such an application, data might be stored and retrieved from one or more blockchains by distributed network nodes without relying on centralized coordination and trusted third parties. Data access could be provided through a query language such as SQL at the application level, establishing a unified view on application-level data that is verifiably stored. However, when accessing multiple blockchains through their node software and APIs, interoperability cannot be assumed today, resulting in challenges of inhomogeneous data access. In addition, different feature sets and trade-offs exist, e.g., regarding smart contract functionality, availability, distribution, scalability, and security. For increasing interoperability, the paper at hand suggests pursuing the development of a cross-chain query language at the application level. The language abstracts from implementation by providing a standardized syntax, an integrated data model, and a processing architecture for data queries. This research is an extended and updated paper of a prior publication demonstrating the language syntax, data model, and architecture with an evaluation of compatibility against the largest open and permissionless blockchains today.