FHIR Mapping Language (FML), published by HL7 International / FHIR Infrastructure. This guide is not an authorized publication; it is the continuous build for version 0.1.0 built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of https://github.com/HL7/mapping-language-ig/ and changes regularly. See the Directory of published versions

StructureMap:

Example demonstrating the id transform to create an Identifier

/// url = 'http://hl7.org/fhir/uv/mapping-language/StructureMap/TransformId'
/// name = 'TransformId'
/// status = 'active'
/// description = 'Example demonstrating the id transform to create an Identifier'

uses "http://hl7.org/fhir/StructureDefinition/Patient" as source
uses "http://hl7.org/fhir/StructureDefinition/Patient" as target

group TransformId(source src : Patient, target tgt : Patient) {
  src -> tgt.identifier = id('http://example.org/ids', '12345') "r1";
}