Semantic Modelling and Linked Open Data (LOD) is fundamental to the German National Research Data Infrastructure (NFDI) to FAIRify and interconnect data within the Research Data Management Process. This implements the Open Science Idea and the FAIR data principles to create re-usable research (meta-)data according to the four LOD rules:

1. Use URIs as names for things.
2. Use HTTP URIs so that people can look up those names.
3. When someone looks up a URI, provide useful information, using the standards (RDF, SPARQL).
4. Include links to other URIs, so that more information can be discovered.

One of the main goals of the NFDI initiatives is to interlink and perform knowledge transfer within the different Communities of Practices on Semantic Modelling and Linked Open Data to create sustainable methods and services.

The NFDI4Objects Community Cluster on Semantic Modelling and LOD focuses on three main topics:

• Semantic modelling practices and Linked Open Data implementations such as ontologies and reference models (e.g. CIDOC CRM, EDM) and structured data in the "Wikimedia Universe" (especially Wikidata and other Wikibase instances).
• fuzzyness & wobbliness: what is “uncertainty”, modelling strategies (RDF/RDF*), benefits
• dating: relative vs. absolute dating mechanisms, uncertainties and vagueness, hidden assumptions, definition of human-made concepts such as “periods”

The Community Cluster also deals with mapping ontologies and standards for uncertainties and ambiguities. It works closely together with other initiatives and networks such as the CAA, the DHd working group “Graphen & Netzwerke”, the CAA Special Interest Group on Semantics and LOUD in Archaeology (SIG-DataDragon), as well as the grassroots Research Squirrel Engineers network. This Community Cluster covers the parts of the research data lifecycle relating to processing, enrichment and publication. The central topic of this cluster is the interdisciplinary exchange of knowledge in the field of interoperable knowledge modelling of object and collection-related data with the help of semantics to enable FAIR data, especially regarding its traceability and reuse.

This poster shows the main subjects, challenges, and participation opportunities for Semantic Modelers, Linked Open Data enthusiasts, and Ontology Engineers within the NFDI, in cooperation with the Community Cluster Semantic Modelling & LOD, the CAA-DE and CAA International. It serves as a communication point for researchers dealing with this topic.