The purpose of the European OpenAIRE infrastructure is to facilitate, foster, support, and monitor Open Science scholarly communication in Europe. The infrastructure has been operational for almost a decade and successful in linking people, ideas and resources in support of the free flow, access, sharing, and re-use of research outcomes. To this aim it offers dissemination and training on Open Access and Open Science, facilitates exchange of knowledge, and operates the technical services required to facilitate and monitor Open Science publishing trends and research impact across geographic and discipline boundaries. OpenAIRE services populate a research graph whose objects are scientific results, organizations, funders, communities, organizations, and data sources. In this article we describe the data model, inspired by several existing metadata standards.