FHIR Mapping

OVF was designed with FHIR alignment in mind but simplifies many structures for the veterinary domain. This guide covers how to convert between the two formats.

Resource mapping overview

OVF Resource	FHIR Resource	Key Differences
Patient	Patient	OVF adds species, breed, breed_code as top-level fields; FHIR uses extensions. OVF has flat owner object; FHIR uses separate RelatedPerson.
Encounter	Encounter	OVF uses 4 status values (vs FHIR’s 9). Flat practitioner instead of participant array with role coding.
Condition	Condition	Nearly identical. OVF uses simpler code systems (icd-10-vet, snomed-ct-vet) instead of full CodeableConcept.
Observation	Observation	OVF uses a flexible value field; FHIR uses typed value[x] (valueQuantity, valueString, etc.).
Immunization	Immunization	OVF adds next_dose_date and expiration_date as first-class fields.
Procedure	Procedure	OVF adds a dedicated anesthesia sub-object. FHIR models this as a separate resource or extension.
AllergyIntolerance	AllergyIntolerance	OVF simplifies reaction to a single object; FHIR allows an array of reactions.
MedicationStatement	MedicationStatement	OVF simplifies dosage to a flat object; FHIR uses the complex Dosage backbone element.
DocumentReference	DocumentReference	OVF uses direct url, data, content_type fields; FHIR nests content in content[].attachment.

OVF to FHIR conversion

Patient

• Species/breed: FHIR has no native species/breed on Patient. Use the patient-animal extension:

{
  "resourceType": "Patient",
  "extension": [
    {
      "url": "http://hl7.org/fhir/StructureDefinition/patient-animal",
      "extension": [
        {
          "url": "species",
          "valueCodeableConcept": {
            "coding": [{ "system": "http://snomed.info/sct", "code": "448771007", "display": "Canis lupus familiaris" }]
          }
        },
        {
          "url": "breed",
          "valueCodeableConcept": {
            "coding": [{ "system": "http://fci.be", "code": "166", "display": "Labrador Retriever" }]
          }
        }
      ]
    }
  ]
}

• Identifiers: OVF system enum values expand to full URIs:

OVF System	FHIR Identifier System URI
iso-microchip-11784	urn:oid:2.16.840.1.113883.4.3xx or http://hl7.org/fhir/sid/microchip
eu-pet-passport	http://ec.europa.eu/food/animals/pet-movement/eu-pet-passport
safe-animal	https://www.safe-animal.eu
europetnet	https://www.europetnet.com

• Owner: Maps to a FHIR RelatedPerson resource linked via Patient.link or Patient.contact.
• Weight: Maps to a FHIR Observation with LOINC code 29463-7 (Body weight).

Encounter

• Status: OVF 4 values map directly where they overlap with FHIR’s 9.
• Practitioner: Flat practitioner maps to Encounter.participant[].individual referencing a Practitioner resource.
• Diagnoses: Array of condition IDs maps to Encounter.diagnosis[].condition as Reference(Condition).

Observation

OVF’s polymorphic value must be mapped to the appropriate FHIR value[x]:

OVF value type	FHIR field
number	valueQuantity (with unit)
string	valueString
boolean	valueBoolean
object	valueCodeableConcept or valueQuantity

Procedure

FHIR has no native anesthesia sub-object. Options:

• Create a separate FHIR Procedure for the anesthesia
• Use an extension on the Procedure resource
• Record as a MedicationAdministration linked to the Procedure

MedicationStatement

OVF’s flat dosage maps to FHIR dosage[]:

• value + unit becomes dosage[].doseAndRate[].doseQuantity
• frequency becomes dosage[].timing.code or timing.repeat
• route becomes dosage[].route CodeableConcept

FHIR to OVF conversion

General approach

1. Map FHIR resource types to OVF equivalents using the table above
2. Flatten complex FHIR structures (CodeableConcept, Reference, Dosage) into OVF’s simpler fields
3. Use the first coding from any CodeableConcept array as the OVF code value
4. Drop FHIR metadata fields with no OVF equivalent (meta, text, contained, extension unless mapped)

Data loss (FHIR to OVF)

The following FHIR data may be lost or simplified:

• Multiple codings: FHIR CodeableConcept can have multiple codings; OVF retains only one
• Complex timing: Dosage timing with repeat patterns simplifies to a free-text frequency string
• Participant roles: FHIR typed participant roles reduce to a single practitioner
• Multiple reactions: FHIR’s array of reactions reduces to a single reaction object
• Resource references: FHIR typed references become flat objects or string IDs
• Provenance/audit: meta.lastUpdated, meta.source, provenance chains have no OVF equivalent
• Narrative text: FHIR text (XHTML narrative) is not preserved

Data loss (OVF to FHIR)

• Species/breed: Must be mapped to FHIR extensions
• Anesthesia sub-object: Must be modeled as a separate resource or extension
• next_dose_date: Must be mapped to ImmunizationRecommendation or an extension
• Owner as nested object: Must be extracted into a separate RelatedPerson resource
• x_ extensions: Custom OVF fields should map to FHIR extensions with appropriate URIs

Date format compatibility

Both OVF and FHIR use ISO 8601. No conversion needed for temporal fields, with one caveat:

• OVF date fields: YYYY-MM-DD (strict)
• OVF datetime fields: YYYY-MM-DDThh:mm:ssZ (strict)
• FHIR dateTime supports partial dates (2025, 2025-06) — these must be expanded to full precision when converting to OVF

When to use FHIR vs OVF

Use case	Recommended format
Interop with human healthcare / hospital systems	FHIR
Veterinary clinic-to-clinic data exchange	OVF
Pet health apps in the Polish/CEE market	OVF
AI/LLM structured output for vet records	OVF
Regulatory compliance (EU Pet Passport data)	OVF with Polish extensions
Academic research requiring full clinical detail	FHIR