The Digital Open Marketplace Ecosystem (DOME) 4.0 aims at developing a comprehensive industrial data ecosystem aligned with the Open Science and Open Innovation objectives to enable sharing of business-to-business (B2B) data for the purpose of value generation and creation of new or enhanced products, processes, and services. DOME 4.0 will be open to all providers and users of data, and aims to facilitate maximum knowledge extraction with the help of ontology-driven semantic data interoperability and modern data processing technologies adopted from the fields of Machine Learning (ML) and Artificial Intelligence (AI). These features are crucial to scale and advance the proposed ecosystem to any sector of the economy. Given the significant contribution of the materials and manufacturing sectors to the European economy, DOME 4.0 focuses on data-driven knowledge generation within these key sectors. The project duration is four years and will focus on two parts: a) core ecosystem technology advancement with connectors to other marketplaces, data and knowledge bases; and b) demonstration of added value via nine B2B success stories covering areas such as nanomaterials, manufacturing equipment and processes, lightweight construction, etc., while dealing with data characteristics such as quantity, quality, velocity, formats, and sources. Data governance, sovereignty, provenance and adherence to FAIR principles are proposed. True to its ethos, DOME 4.0 offers a scalable, convergence mechanism to the vast array of research and innovation activities undertaken within the Horizon 2020 programme. The project coalesces the key H2020 developments from multiple marketplace projects, open simulation platforms, open translation environments, industrial networks, data platforms, and Coordination and Support Actions in advanced materials and manufacturing. Central to DOME 4.0 is its interdisciplinary consortium with European SMEs, large industries, research institutes and academia.