Advancing data management in local energy trading: European policy, state-of-the-art, and real-world practice in FEDECOM and STUNNED

<ns3:p>This Open Letter reflects on best practices for data management in energy exchange and trading in the context of European energy communities. It draws on European policy developments, selected literature, and practical experience from two Horizon Europe projects, FEDECOM and STUNNED, to highlight recurring challenges and emerging solutions related to interoperability, data governance, security, and scalability. Rather than presenting original empirical results, the paper adopts a practice-oriented perspective, using these projects as illustrative examples to bridge policy objectives, technical approaches, and real-world implementation. The intended audience includes researchers, technology providers, project developers, and policymakers involved in the digitalisation of energy systems. The Open Letter concludes with concrete recommendations and future research directions aimed at supporting interoperable, data-driven energy trading across Europe.</ns3:p>