The German National Library (DNB) operates the DNB SPARQL Service, powered by the QLever SPARQL engine, providing standardized RDF‑based semantic queries over national bibliographic and authority data. Fully compliant with the SPARQL 1.1 standard, the service supports both automated and manual queries through its API, with results viewable in a user interface or exportable in multiple formats.

At its core, this Knowledge Graph offers a uniquely consistent representation of national bibliographic entities – dating back to 1913 – and their connections to authority records in the Integrated Authority File (GND). It is openly accessible: users, from researchers to the interested public, can explore curated sets of publications linked to people, places, or keywords within selected timeframes, among many other possibilities. This openness and quality enable the DNB SPARQL Service to be integrated into the KGI4NFDI (Knowledge Graph Infrastructure for the NFDI), one of the Base4NFDI basic services.

KGI4NFDI supports the creation, reuse, and registry of knowledge graphs across the NFDI, providing shared documentation, guidance, and software. Its mission is to improve data integration, promote standardized ontological practices, and operationalize the FAIR principles (Wilkinson et al. 2016) across disciplines. Federation is a key feature: SPARQL endpoints can be connected so that queries span multiple KGs simultaneously, retrieving distributed data in a unified manner – without sacrificing autonomy or structure. Such infrastructures of engagement – open, inclusive, collaborative, and sustainable – ensure that valuable curated datasets do not remain isolated but become interconnected assets in a shared research ecosystem.

Within the NFDI, the DNB contributes to the Text+ consortium, which aggregates, curates, and disseminates language‑ and text‑based research data for the humanities. Here, the DNB brings in its bibliographic and authority data expertise and actively transfers knowledge related to KG technologies. Text+ also hosts a dedicated GND agency (Buddenbohm et al. 2023), run collaboratively by DNB and Göttingen State and University Library, to support the use and expansion of authority data across disciplines. While not yet directly linked to the DNB Knowledge Graph, this initiative strengthens interoperability and offers future opportunities for integration. By linking the DNB SPARQL Service to KGI4NFDI, Text+ itself becomes connected to this NFDI‑wide federated KG infrastructure, opening further opportunities for cross‑domain data enrichment, interoperability, and collaboration. These interconnections also create fertile ground for co‑creation, citizen science, public and participatory humanities, and community‑driven scholarship – engaging not only academic institutions but also a wider public in the stewardship and creative reuse of cultural and scholarly data.

This poster will illustrate how knowledge graph technology – combined with open architectural concepts – enables effective knowledge transfer across networks, enriching authoritative data for multiple domains. Live demonstrations will showcase the strengths of the DNB SPARQL Service and highlight its role as a bridge between the public, the humanities research community, and the wider NFDI infrastructure.