Metadata pointing at a Composition

{
  "resourceType": "DocumentReference",
  "id": "example-composition",
  "meta": {
    "security": [
      {
        "system": "http://terminology.hl7.org/CodeSystem/v3-ActReason",
        "code": "HTEST"
      }
    ]
  },
  "text": {
    "status": "generated",
    "div": "<div xmlns=\"http://www.w3.org/1999/xhtml\"><p><b>Generated Narrative: DocumentReference</b><a name=\"example-composition\"> </a></p><div style=\"display: inline-block; background-color: #d9e0e7; padding: 6px; margin: 4px; border: 1px solid #8da1b4; border-radius: 5px; line-height: 60%\"><p style=\"margin-bottom: 0px\">Resource DocumentReference &quot;example-composition&quot; </p><p style=\"margin-bottom: 0px\">Security Labels: <span title=\"{http://terminology.hl7.org/CodeSystem/v3-ActReason http://terminology.hl7.org/CodeSystem/v3-ActReason}\">http://terminology.hl7.org/CodeSystem/v3-ActReason</span></p></div><p><b>identifier</b>: id: 1</p><p><b>status</b>: current</p><p><b>type</b>: Consult note <span style=\"background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki\"> (<a href=\"https://loinc.org/\">LOINC</a>#11488-4)</span></p><p><b>category</b>: Report <span style=\"background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki\"> (<a href=\"https://loinc.org/\">LOINC</a>#LP173421-1)</span></p><p><b>subject</b>: <a href=\"patient-example-xcda.html\">Patient/xcda: Henry Levin the 7th</a> &quot;Henry LEVIN&quot;</p><p><b>context</b>: <a href=\"encounter-example-xcda.html\">Encounter/xcda</a></p><h3>Events</h3><table class=\"grid\"><tr><td>-</td><td><b>Concept</b></td><td><b>Reference</b></td></tr><tr><td>*</td><td>health record <span style=\"background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki\"> (<a href=\"http://terminology.hl7.org/3.1.0/CodeSystem-v3-ActCode.html\">ActCode</a>#HEALTHREC)</span></td><td> </td></tr><tr><td>*</td><td> </td><td><a href=\"observation-example.html\">Observation/example</a></td></tr></table><p><b>period</b>: 2010-07-18 --&gt; 2012-11-12</p><p><b>date</b>: 04/01/2012 8:10:14 PM</p><p><b>author</b>: <a href=\"practitioner-example-xcda-author.html\">Practitioner/xcda-author: Harold Hippocrates, MD</a> &quot;Harold HIPPOCRATES&quot;</p><h3>Attesters</h3><table class=\"grid\"><tr><td>-</td><td><b>Mode</b></td><td><b>Party</b></td></tr><tr><td>*</td><td>Professional <span style=\"background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki\"> (<a href=\"codesystem-composition-attestation-mode.html\">CompositionAttestationMode</a>#professional)</span></td><td><a href=\"practitioner-example-xcda-author.html\">Practitioner/xcda-author: Harold Hippocrates, MD</a> &quot;Harold HIPPOCRATES&quot;</td></tr></table><h3>RelatesTos</h3><table class=\"grid\"><tr><td>-</td><td><b>Code</b></td><td><b>Target</b></td></tr><tr><td>*</td><td>Replaces <span style=\"background: LightGoldenRodYellow; margin: 4px; border: 1px solid khaki\"> (<a href=\"codesystem-document-relationship-type.html\">DocumentRelationshipType</a>#replaces)</span></td><td><a href=\"broken-link.html\">DocumentReference/old-example</a></td></tr></table><p><b>description</b>: Example of a Comprehensive DocumentReference resource. This is fully filled for all mandatory elements and all optional elements.</p><blockquote><p><b>content</b></p><h3>Attachments</h3><table class=\"grid\"><tr><td>-</td><td><b>Url</b></td></tr><tr><td>*</td><td><code>Composition/example</code></td></tr></table></blockquote></div>"
  },
  "identifier": [
    {
      "system": "http://healthintersections.com.au/test",
      "value": "1"
    }
  ],
  "status": "current",
  "type": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "11488-4",
        "display": "Consult note"
      }
    ]
  },
  "category": [
    {
      "coding": [
        {
          "system": "http://loinc.org",
          "code": "LP173421-1",
          "display": "Report"
        }
      ]
    }
  ],
  "subject": {
    "reference": "Patient/xcda",
    "display": "Henry Levin the 7th"
  },
  "context": [
    {
      "reference": "Encounter/xcda"
    }
  ],
  "event": [
    {
      "concept": {
        "coding": [
          {
            "system": "http://terminology.hl7.org/CodeSystem/v3-ActCode",
            "code": "HEALTHREC",
            "display": "health record"
          }
        ]
      }
    },
    {
      "reference": {
        "reference": "Observation/example"
      }
    }
  ],
  "period": {
    "start": "2010-07-18",
    "end": "2012-11-12"
  },
  "date": "2012-01-04T09:10:14Z",
  "author": [
    {
      "reference": "Practitioner/xcda-author",
      "display": "Harold Hippocrates, MD"
    }
  ],
  "attester": [
    {
      "mode": {
        "coding": [
          {
            "system": "http://hl7.org/fhir/composition-attestation-mode",
            "code": "professional"
          }
        ]
      },
      "party": {
        "reference": "Practitioner/xcda-author",
        "display": "Harold Hippocrates, MD"
      }
    }
  ],
  "relatesTo": [
    {
      "code": {
        "coding": [
          {
            "system": "http://hl7.org/fhir/document-relationship-type",
            "code": "replaces"
          }
        ]
      },
      "target": {
        "reference": "DocumentReference/old-example"
      }
    }
  ],
  "description": "Example of a Comprehensive DocumentReference resource. This is fully filled for all mandatory elements and all optional elements.",
  "content": [
    {
      "attachment": {
        "url": "Composition/example"
      }
    }
  ]
}