http://hl7.org/fhir/StructureDefinition/MessageHeader|4.0.1

The header for a message exchange that is either requesting or responding to an action. The reference(s) that are the subject of the action as well as other information related to the action are typically transmitted in a bundle in which the MessageHeader resource instance is the first resource in the bundle.
{
  "description": "The header for a message exchange that is either requesting or responding to an action.  The reference(s) that are the subject of the action as well as other information related to the action are typically transmitted in a bundle in which the MessageHeader resource instance is the first resource in the bundle.",
  "package": "hl7.fhir.r4.core@4.0.1",
  "date": "2019-10-31T22:29:23Z",
  "derivation": "specialization",
  "meta": {
    "lastUpdated": "2019-11-01T09:29:23.356+11:00"
  },
  "publisher": "Health Level Seven International (Infrastructure And Messaging)",
  "fhirVersion": "4.0.1",
  "purpose": "Many implementations are not prepared to use REST and need a messaging based infrastructure.",
  "name": "MessageHeader",
  "mapping": [ {
    "uri": "http://hl7.org/v2",
    "name": "HL7 v2 Mapping",
    "identity": "v2"
  }, {
    "uri": "http://hl7.org/v3",
    "name": "RIM Mapping",
    "identity": "rim"
  }, {
    "uri": "http://hl7.org/fhir/fivews",
    "name": "FiveWs Pattern Mapping",
    "identity": "w5"
  } ],
  "abstract": false,
  "type": "MessageHeader",
  "experimental": null,
  "resourceType": "StructureDefinition",
  "fhirversion": null,
  "title": null,
  "versionAlgorithmCoding": null,
  "extension": [ {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-category",
    "valueString": "Foundation.Other"
  }, {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status",
    "valueCode": "trial-use"
  }, {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-fmm",
    "valueInteger": 4
  }, {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-security-category",
    "valueCode": "not-classified"
  }, {
    "url": "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode": "inm"
  } ],
  "status": "draft",
  "id": "84f9dd35-cf49-5c11-82d2-8bd8f998292d",
  "kind": "resource",
  "url": "http://hl7.org/fhir/StructureDefinition/MessageHeader",
  "identifier": null,
  "versionAlgorithmString": null,
  "fhir_id": null,
  "version": "4.0.1",
  "contact": [ {
    "telecom": [ {
      "value": "http://hl7.org/fhir",
      "system": "url"
    } ]
  }, {
    "telecom": [ {
      "value": "http://www.hl7.org/special/committees/inm/index.cfm",
      "system": "url"
    } ]
  } ],
  "baseDefinition": "http://hl7.org/fhir/StructureDefinition/DomainResource"
}