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FHIR mapping & round-trip fidelity

This page describes, at a high level, what FHIR the builder speaks and how faithfully it preserves a questionnaire through import and export.

What it targets

The builder authors FHIR Questionnaire resources and can target R4, R4B or R5, selected from the toolbar version selector. On import the version is auto-detected from the builder's own marker or R5-only fields (otherwise R4), and STU3 input is adapted to R4. See Import & round-trip.

On top of base FHIR it supports a broad set of SDC (Structured Data Capture) extensions — expressions, dynamic options, rendering hints, extra validation and more. Those are grouped and explained in Extensions & SDC, and listed field-by-field in the FHIR field reference.

The runtime is real FHIR

The preview is a working SDC runtime, not a mock-up: it evaluates FHIRPath, resolves enableWhen / enableWhenExpression, runs calculatedExpression and initialExpression, and produces a valid QuestionnaireResponse. So what you see in the preview reflects how a conformant SDC client would behave.

Round-trip fidelity

The builder is built to avoid silently changing questionnaires:

  • Fields and extensions it understands are surfaced in the UI and written back on export.
  • Extensions it does not specifically render are preserved on import and re-emitted on export, rather than dropped.

This means you can import a questionnaire, make a focused edit, and export it again with confidence. Where a conversion is inherently lossy — most notably REDCap import/export, since REDCap and FHIR are different models — the builder tells you what doesn't map cleanly instead of hiding it.

Where the authoritative list lives

For the exhaustive, current list of supported fields and extensions, use the in-app FHIR field reference; the project also maintains a detailed FHIR mapping document in its source repository.

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