The Consortium of European Social Science Data Archives CESSDA is a distributed European Infrastructure with 15 member countries (www.cessda.eu). CESSDA, wants to be a key player in social science infrastructures, providing a trusted platform with tools and services to publish and re-use research data in a safe and secure way. Key features of platforms are that they focus on interactions between producers and users, the service providers do not own the assets, and the focus is on the users – platforms are demand-oriented. Successful platforms have viable business models and from the interactions they generate business information and turn this into value. Traditional data services have a focus on ingest, archiving and serving data producers. The DDI serves this process of taking data in and provide them with metadata. But in a platform-world that is not enough. Users might want to re-use individual data sets, but to tackle grand challenges they need a far more complex system of data that are interlinked. Scientists and machines will perform analyses on these data clusters. Hence, we must also describe the relationships between data within clusters. I will take CESSDA as a case to describe how we work on realising a social science data platform.