Fixed/Pattern Errors

Fixed and pattern errors occur when an element’s value does not match a fixed[x] or pattern[x] constraint declared in the ElementDefinition. These two constraint types serve different purposes:

• fixed[x] – The element value must match the fixed value exactly. No additional properties are allowed beyond what is specified.
• pattern[x] – The element value must contain at least the properties specified in the pattern, but additional properties are permitted.

Error Codes

FIXED_VALUE_MISMATCH

The actual value of the element does not match the fixed value declared in the ElementDefinition. When an element has a fixed[x] constraint, the value in the resource must be identical to the fixed value.

Example – invalid resource:

A profile sets Observation.status to a fixed value of "final":

{
  "id": "Observation.status",
  "path": "Observation.status",
  "fixedCode": "final"
}

A resource that violates this constraint:

{
  "resourceType": "Observation",
  "status": "preliminary",
  "code": {
    "coding": [{ "system": "http://loinc.org", "code": "85354-9" }]
  }
}

Validation output:

ERROR: Value 'preliminary' does not match fixed value 'final'
  Path: Observation.status
  MessageID: FIXED_VALUE_MISMATCH

Fix: Use the exact value specified by the profile:

{
  "resourceType": "Observation",
  "status": "final",
  "code": {
    "coding": [{ "system": "http://loinc.org", "code": "85354-9" }]
  }
}

Fixed Values on Complex Types

Fixed values can also apply to complex types. In this case, every property in the fixed value must match exactly:

{
  "id": "Observation.code",
  "path": "Observation.code",
  "fixedCodeableConcept": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "85354-9"
      }
    ]
  }
}

The resource must include exactly the same coding with no additional codings or properties.

PATTERN_MISMATCH

The element’s value does not include all the properties specified in the pattern. Unlike fixed values, patterns only require that the specified properties are present with the correct values – additional properties are allowed.

Example – invalid resource:

A profile defines a pattern on Observation.code:

{
  "id": "Observation.code",
  "path": "Observation.code",
  "patternCodeableConcept": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "85354-9"
      }
    ]
  }
}

A resource that violates this pattern:

{
  "resourceType": "Observation",
  "status": "final",
  "code": {
    "coding": [
      {
        "system": "http://snomed.info/sct",
        "code": "271649006"
      }
    ]
  }
}

The pattern requires a coding with system http://loinc.org and code 85354-9, but the resource only contains a SNOMED coding.

Validation output:

ERROR: Value does not match required pattern at 'Observation.code'
  Path: Observation.code
  MessageID: PATTERN_MISMATCH

Fix: Include the required pattern coding (additional codings are allowed):

{
  "resourceType": "Observation",
  "status": "final",
  "code": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "85354-9",
        "display": "Blood pressure panel"
      },
      {
        "system": "http://snomed.info/sct",
        "code": "271649006",
        "display": "Systemic arterial pressure"
      }
    ]
  }
}

Key Differences Between Fixed and Pattern