FHIR System Search Parameters

The HL7 FHIR standard defines system search parameters that apply across all resource types. Burni v3 provides full native support and MongoDB query optimization for these parameters.

1. _tag: Filtering by Meta Tags

Find resources associated with specific category or metadata tags (Resource.meta.tag):

GET [baseUrl]/Patient?_tag=http://example.org/codes|VIP
GET [baseUrl]/Observation?_tag=critical

Multiple Tag Combinations

• Comma separated (_tag=a,b): Logical OR
• Repeated parameters (_tag=a&_tag=b): Logical AND

GET [baseUrl]/Patient?_tag=http://example.org|tagA&_tag=http://example.org|tagB

2. _security: Security Labels

Filter resources based on their confidentiality classification or access constraints (Resource.meta.security):

GET [baseUrl]/DocumentReference?_security=http://terminology.hl7.org/CodeSystem/v3-ActCode|R

Ideal for multi-tenant isolation, role-based filtering, and compliance auditing.

3. _profile: Profile Conformance

Query resources conforming to a designated StructureDefinition Canonical URI (Resource.meta.profile):

GET [baseUrl]/Patient?_profile=http://hl7.org/fhir/us/core/StructureDefinition/us-core-patient

4. Full Date & Timezone Offset Precision

FHIR date searches require strict interval calculation depending on the parameter format:

• Prefixes: eq, ne, gt, lt, ge, le, sa, eb, ap.
• Timezone Offsets: Handles UTC offsets (+08:00, -05:00, Z) accurately.
• Varying Precision: Searches using year (ge2026) or month (2026-09) automatically expand to exact start and end millisecond ranges, preventing false negatives.

Examples:

GET [baseUrl]/Appointment?date=ge2026-09-01&date=le2026-09-30
GET [baseUrl]/Observation?date=gt2026-09-12T00:00:00+08:00