dc.description.abstract | Data is becoming an indispensable production factor for the modern economy, matching or exceeding in importance traditional factors such as land, infrastructure, labor and capital. As part of this, a wide range of applications in different sectors require huge amounts of information to feed machine learning models and algorithms responsible for critical roles in production chains and business processes. A variety of data trading entities including, but not limited to data marketplaces, have thus appeared in order to satisfy and match the offer with the demand for data. In this paper, we present the results and conclusions from a comprehensive survey covering 190 commercial data trading entities, the types of data that their trade, as well as their business models and the technologies that they rely upon. We also point to promising open research questions in the areas of data marketplace federation, pricing, and data ownership protection that could benefit the growing ecosystem of data trading entities that we have surveyed. | es |