NamingSystem Examples

ℹ️ For concepts, the Philippine NamingSystem registry, and the Patient identity use case, see NamingSystem in PH Core. This page has the diagrams.

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FHIR NamingSystem — Model and Examples

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Overview

FHIR relies heavily on globally unique system identifiers (URIs) to distinguish business identifiers (e.g. MRN, PhilHealth PIN, PhilSys ID) from terminology systems (e.g. SNOMED CT, LOINC). A URI alone is not self-describing — the NamingSystem resource is the governed metadata layer that says what a URI actually means.

The critical join between any FHIR instance and the NamingSystem registry:

Identifier.system == NamingSystem.uniqueId.value

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Example: Terminology system (SNOMED CT)

flowchart LR
    A["Coding
    system = http://snomed.info/sct
    code = 22298006"]

    B[NamingSystem: SNOMED CT]

    C["URI:
    http://snomed.info/sct"]

    A --> B
    B --> C

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Example: PhilHealth Identification Number (PIN)

flowchart LR
    A["Patient.identifier
    system = http://philhealth.gov.ph/fhir/Identifier/philhealth-id
    value = 12-345678901-2"]

    B["NamingSystem: PhilHealthID
    publisher = PhilHealth
    kind = identifier"]

    C["URI:
    http://philhealth.gov.ph/fhir/Identifier/philhealth-id"]

    A --> B
    B --> C

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Example: PhilSys Identification Number

flowchart LR
    A["Patient.identifier
    system = http://philsys.gov.ph/fhir/Identifier/philsys-id
    value = 1234-5678-9101-1213"]

    B["NamingSystem: PhilSysID
    publisher = PSA
    kind = identifier"]

    C["URI:
    http://philsys.gov.ph/fhir/Identifier/philsys-id"]

    A --> B
    B --> C

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Example: Layered identifiers in a Patient Client Registry

A single Patient resource can carry identifiers from multiple agencies simultaneously. All are valid under the open-sliced PHCorePatient profile.

flowchart LR
    P["Patient
    (FHIR instance)"]

    P -->|identifier[0]| A["Patient.identifier
    system = .../philsys-id
    value = 1234-5678-9101-1213"]

    P -->|identifier[1]| B["Patient.identifier
    system = .../philhealth-id
    value = 12-345678901-2"]

    P -->|identifier[2]| C["Patient.identifier
    system = .../hospital-mrn
    value = MRN-00001"]

    A --> NS1["NamingSystem: PhilSysID
    publisher = PSA"]

    B --> NS2["NamingSystem: PhilHealthID
    publisher = PhilHealth"]

    C --> NS3["open slice
    no NamingSystem required
    (can be added later)"]

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Example: Multiple unique identifiers for the same system (URI + OID)

A NamingSystem can record multiple representations of the same identifier system — useful for legacy integration and HL7 v2 ↔ FHIR transformation.

flowchart LR
    A["Patient Identifier
    system = http://hospital.example.org/mrn
    value = 123456"]

    B[NamingSystem: Hospital MRN]

    C["URI:
    http://hospital.example.org/mrn"]

    D["OID:
    1.2.36.146.595.217.0.1"]

    A --> B
    B --> C
    B --> D

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Conceptual model

classDiagram

class Identifier {
  system : uri
  value : string
}

class Coding {
  system : uri
  code : string
}

class NamingSystem {
  url : uri
  name : string
  kind : code
}

class NamingSystemUniqueId {
  type : code
  value : string
  preferred : boolean
}

Identifier --> NamingSystem : resolves system
Coding --> NamingSystem : resolves system
NamingSystem --> NamingSystemUniqueId

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