Complementary, not replacement
Transporting clinical data is not the same as transporting a trustworthy clinical document.
| Layer | Purpose |
|---|---|
| HL7 / FHIR / CDA | Healthcare-specific structure, exchange and clinical semantics. |
| Rendered clinical document | A stable human-readable presentation for a clinical or administrative purpose. |
| Provenance and revision history | Source, author, creation, revision, addendum and derivation context. |
| Document identity and finality | Which exact document state is being referenced or verified. |
| UD | A potential portable substrate joining readable presentation, lineage and exact-state verification. |
UD does not replace HL7, FHIR, CDA, EHR-native exchange or their mature clinical ecosystems.