Understand C-CDA on FHIR mapping concepts for translating document sections to FHIR resources

Verified steps

1. Review the HL7 C-CDA on FHIR IG, which defines FHIR Composition profiles that mirror C-CDA document types (CCD, Discharge Summary, Progress Note, etc.) and provides mappings between C-CDA sections/entries and FHIR resource types.
2. Understand the mapping pattern: each C-CDA section (identified by LOINC section code) maps to a Composition.section with the same LOINC code, and the C-CDA entries within that section map to FHIR resources (e.g., Problem Section entries map to Condition resources, Medications Section entries map to MedicationStatement or MedicationRequest resources).
3. For translating C-CDA to FHIR: parse the C-CDA XML to extract section content and entries, map entries to FHIR resources using the IG's mapping tables, and assemble a FHIR document Bundle with a Composition resource and all mapped resources.
4. For translating FHIR to C-CDA: take the FHIR Composition and its referenced resources, apply the reverse mapping, and generate C-CDA XML with the correct templateIds, section codes, and entry structures.
5. Recognize that some C-CDA content (narrative text, complex clinical models) may not have direct FHIR equivalents, and some FHIR resources may not map cleanly to C-CDA entries — plan for lossy translation in edge cases.
6. Validate translated documents against both the source format's constraints and the target format's profile (C-CDA Schematron or FHIR validator) to confirm translation fidelity.