This product consists of the XML schema and the JSON schema aligned with the Scholix Metadata Guidelines Version 4. It contains the .json and /xsd files together with examples of compatible metadata records. Changes from the previous update are backward compatible and include the following: The schema admits for the field type (typology of source/target objects) terms of the following vocabulary: publications, datasets, software, other research types (version 3.0 included only literature and dataset) The schema includes a new optional field subtype which includes the specific sub-type of the objects, according to the OpenAIRE classification of publications, datasets, software, and other products (for more) The schema admits multiple entries for the field Identifier in both the source and target objects; this is to specify the list of PIDs resulting from the deduplication on OpenAIRE (i.e. the same publication may have been collected from Crossref and from EuropePMC, thus including both PIDs).