Fig. 1From: QL4MDR: a GraphQL query language for ISO 11179-based metadata repositoriesUsing metadata to support the integration of healthcare instance data. The process consists of the four stages: the metadata acquisition stage with a uniform interface enables to reuse of information which is stored in project-specific MDRs. The matching stage aligns the metadata and identifies potential correspondences. The mapping stage creates transformation rules, which are used in the transformation stage. The first three stages only process metadata, whereas the last transformation stage includes healthcare instance dataBack to article page