Technical specification for Health Data Access Bodies on the national metadata catalogue

This TEHDAS2 technical specification supports the implementation of the European Health Data Space (EHDS).This technical specification provides technical guidance for Health Data Access Bodies (HDABs), data holders and other stakeholders on how to implement and maintain a national metadata catalogue for datasets intended for secondary use under the European Health Data Space (EHDS) regulation. The catalogue is a key component of the broader HealthData@EU infrastructure, supporting the discoverability and interoperability of electronic health data across member states. Although the EHDS regulation formally entered into force on 26 March 2025, detailed operational guidance – particularly concerning HDABs – will be developed in forthcoming implementing acts. This document provides preparatory technical guidance based on the EHDS regulation and the expected scope of forthcoming implementing acts under Article 77(4). The national metadata catalogue serves as the authoritative registry for all dataset descriptions. Article 51 defines data categories; the authoritative registry aspect is established through Articles 60(3), 77(1) and 79(1). By exposing standardised records through a public interface and via the National Contact Point (NCP), the catalogue operationalises the FAIR principles (findable, accessible, interoperable and reusable) and supports metadata discovery across member states. The document is primarily addressed to HDABs, which serve a pivotal function in facilitating the secure and lawful access to health data. It also engages, where appropriate, with health data holders – such as hospitals, research institutions and health authorities – as well as health data users. This technical specification outlines guidance implementing such catalogues, including metadata ingestion (as received from data holders), management, output and access. This specification outlines: Functional requirements for the national metadata catalogue, covering metadata ingestion, validation, versioning, publication, synchronisation with the EU-level catalogue, and user search and retrieval. These requirements are derived directly from the EHDS regulation (notably Articles 57, 73, and 77). Non-functional recommendations, such as minimum availability and performance targets, system scalability, and security considerations, to ensure robust and reliable catalogue operation. A set of user stories that illustrate the perspectives of key stakeholders – HDAB staff, health data holders, and data users – and demonstrate how the catalogue should support their roles. Proposed solutions for implementation, including modular architectures, metadata model alignment (e.g., HealthDCAT-AP), and alignment with the General Data Infrastructure (GDI) and FAIR principles. Good practices and examples from national and European initiatives, such as Health-RI (Netherlands), Healthdata.be (Belgium), and the European Open Data Portal, which illustrate how catalogues can be effectively developed. A risk analysis that identifies potential challenges – such as variability in national implementation, technical capacity gaps, and security risks – and outlines strategies for mitigation. An overview of existing solutions and case studies, such as the HealthData@EU Central Platform, that can support national catalogue development.