Lead by BBMRI-ERIC, WP8 deals with interoperability of actual data in different phases of HealthData@EU User Journey: from a study of different common data models, available terminologies and how to make data interoperability between nodes, to data exchange among HealthData@EU Nodes and ultimately data delivery to the researchers. It also deals with quality controlling and more generally quality assurance mechanisms that are to be implemented by the HealthData@EU Nodes. The subject of federated queries to obtain new metadata, such as aggregate availability data, is addressed through a feasibility study. WP8 has relations with respect to standards recommended and piloted by WP5 and WP6 and will closely work with WP7 on legal matters (aspects for standards, legal bases for data processing).