The NFDI4Memory Data Space and RADAR4Memory. A Federated Infrastructure for Discovering, Accessing, and Reusing Research Data in the Historical Humanities

Historical research covers a wide range of disciplines, from ancient to contemporary history, encompassing related fields such as economic and social history, religious studies, area studies and the philosophy of history. These disciplines often rely on distributed, heterogeneous and historically evolved sources — archival records, digitised documents, structured datasets and annotations — that are stored across memory institutions, research projects and infrastructure services. The NFDI4Memory consortium [1] seeks to overcome the fragmentation of data and services in the historical humanities by integrating them into a coherent, sustainable and FAIR-oriented digital research environment. [2] The NFDI4Memory Data Space [3] is the central technical component in this endeavour. The NFDI4Memory Data Space, developed by the Task Area 3 "Data Services" [1], is a federated and API-driven digital infrastructure designed to provide researchers in the historical humanities with seamless access to heterogeneous research data and data services. Facing the challenge of dispersed data repositories and fragmented access mechanisms, the NFDI4Memory Data Space offers a unified approach to data discovery, access and reuse across institutional and disciplinary boundaries. At the core of this infrastructure lies a knowledge graph (KG) that indexes both research data (Research Data Graph, RDG) and institutions and their services (Research Information Graph, RIG). Institutions participating in the Data Space expose their data and services through a standardised set of web-based interfaces, such as Access, Update, and Query APIs. Researchers can interact with the Data Space via a dedicated web interface, a RESTful query API or a SPARQL endpoint, allowing for both exploratory search and structured queries across the distributed ecosystem. A key component of the Data Space is integrating essential research data services. One of these is RADAR4Memory, a tailored instance of the RADAR repository platform, which functions as a key service within the federation. RADAR4Memory enables sustainable and standards-compliant archiving, publication and dissemination of research data relevant to the historical humanities. By being integrated into the NFDI4Memory data space, RADAR4Memory and its data publications are not only searchable via the KG, but also interoperable with data and services offered by other institutions. This supports the development of complex, cross-institutional research workflows, for instance the combination of project-based indexing efforts and indexing information (source descriptions) from memory institutions such as archives. The poster presents the technical design and implementation strategy of the NFDI4Memory Data Space, highlights its potential for harmonising data access and reuse in historical research and provides an outlook on the planned evolution of RADAR4Memory as a trusted repository service. The NFDI4Memory Data Space is a key step towards building a digitally integrated research environment for memory institutions and historical disciplines by fostering FAIR principles and promoting standardized service interfaces.