The topic of "Clinical Data Repositories" is central to the HiGHmed-platform.
The latest episode of the eHealth Podcast is a compact introduction to the topic and highlights the role of the interoperability standards openEHR and FHIR used in HiGHmed.
It's worth a listen!
https://www.ehealth-podcast.de/folge-136-clinical-data-repository-cdr/