Concept & metadata layer
Defines the care concepts, data-element meanings, relationships, terminology bindings and enterprise definitions that should survive individual implementations. Examples: ISO 13940, ISO/IEC 11179, terminology concept models.
Clinical content & record layer
Structures clinically coherent information for capture and longitudinal use. Examples: PRSB information models, openEHR archetypes/templates, ISO 13606 archetypes.
Analytical & research layer
Normalises or reshapes source information for reporting, cohort discovery, observational research or clinical trials. Examples: OMOP, i2b2, CDISC ODM/SDTM and dimensional models.
Preservation & traceability layer
Retains the source models, versions, mappings, terminology context and representation information needed to understand records after systems and models change.