SoK: Unified Blockchain Data Structure

Over the last 15 years, blockchain technologies have evolved into a heterogeneous ecosystem with numerous practical applications. The diversity of blockchain data models ranging from UTxO-based to account-based systems and evolving towards smart contract platforms - has led to fragmentation in how blockchain data is stored, accessed, and analysed. This heterogeneity hinders interoperability, complicates cross-chain analytics, and limits reproducibility in blockchain research. In this paper, we present a comprehensive study of blockchain data unification, covering a wide range of academic and commercial approaches. We examine their underlying data structures and identify key limitations in existing solutions. Building on these insights, we propose a unified data model that abstracts and flattens token transfer data while capturing the semantics of both UTxO and account-based paradigms. We conclude by outlining future research directions to further validate and extend this model across diverse blockchain ecosystems.