Slidedeck. SciDataCon 2025. International Data Week. Oct 13 – 16, 2025. https://scidatacon.org/event/9/contributions/54/ Interoperability between vocabulary services is essential to enable the discovery, access, and reuse of vocabularies across diverse domains. Federation of vocabulary services is achieved through API-level and UI-level integration, supporting seamless data sharing and a unified user experience. However, there are many challenges in federating vocabulary services and the semantic resources they deliver. A high-priority task is surfacing the operational services currently available and understanding how these differ, and why. Dedicated programs of work are required to progress the vision of vocabulary services federation. Solutions that work toward achieving this vision are likely to be multifaceted. This session explored the required scope and evaluation criteria for a general solution and examine how several initiatives meet these requirements. The problem space was introduced for a federated ecosystem of vocabulary services, including Semantic Artifact Catalogues (SACS), which are essential for enabling FAIR data. Initiatives and solutions were introduced including FAIR-IMPACT, a European project within the EOSC program, which identified and studied three complementary technical approaches to SAC interoperability. Each approach offers distinct benefits and trade-offs. Discussion included reflections on strategy, collaboration, challenges and next steps for advancing the interoperablity and federation of vocabulary services.