The aim of the Ecosystem Ontology [1] is to provide a light formal vocabulary to support the integration of multiple web-based sources of data and services, in the area of materials and manufacturing. It includes concepts such as: platform, catalogue, dataset, service, topic, and offerin, and is aligned to the EMMO. It complements the Semantic Data Exchange Ontology, where concepts from DCAT are mapped to the richer framework of EMMO. The Ecosystem Ontology is used by core components of the DOME 4.0 platform, as the front end user interface (e.g., the available filtering options and fields for registration), the semantic broker , and connectors to other platforms. Whenever possible, pre existing assets, including formal semantic artefacts and standard knowledge sources (e.g., books) have been re used, including: EuroSciVoc , RoMM , DCAT, MSM, EVMPO and the FAIRsharing Data formats catalogue.