The document discusses data interoperability across the data value chain. It aims to have a common understanding of key aspects of data interoperability and how it is fundamental to data quality and a precondition for open data. Data interoperability is challenging due to divergent needs, capabilities, protocols and fragmented systems. The document outlines several facets of achieving interoperability, including having the right data governance and management, using common data and metadata models, standardized classifications and vocabularies, as well as open data formats and standard interfaces.