Orchestrating Research Infrastructures Services through OAI-PMH: The OPERAS-IT Approach within H2IOSC

Since March 2023, CNR-ILIESI and the Italian node of the OPERAS research infrastructure have led the feasibility study, architectural design, and technical specification for the H2IOSC Marketplace, including the definition of its service orchestration model. This paper presents the conceptual framework for service orchestration in the H2IOSC Marketplace, a federated platform connecting four European research infrastructures in the Social Sciences and Humanities (SSH): OPERAS, E-RIHS, CLARIN, and DARIAH. The orchestration model, conceived and developed by the OPERAS-IT, introduces a two-level integration approach: metadata-level interoperability through OAI-PMH 2.0 harvesting, and service-level orchestration through API-driven workflow management. A key conceptual contribution is the formalization of the distinction between orchestration – where the Marketplace coordinates services executing remotely on distributed infrastructure environments – and composition – where services execute locally within a single platform. This distinction reflects the multi-layered nature of federated research ecosystems and enables composed workflows to participate as meta-services in broader cross-infrastructure orchestration scenarios. We document the complete development timeline of the orchestration concept, from the initial prototypal definition (April 2023) through the technical specification (June 2023), the Zenodo publication (November 2024), and the operational deployment (March 2026). The framework represents the principal element of innovation of the H2IOSC Marketplace with respect to existing marketplace models in federated platforms and Open Science Clouds.