How to connect entries in a FHIR bundle resource belonging to the same time?

Question

For example for an 'Observation' resource I want to have a bundle for 'blood pressure' observation, which will include 'systolic' and 'diastolic'. In the bundle I have observations for multiple dates. How can I connect 'systolic' and 'diastolic' observations belonging to the same date?

{
  "resourceType": "Bundle",
  "title": "Multiple observations",
  "link": [
    {
      "rel": "self",
      "href": "http://localhost:3000/api/users/1/observations/bloodPressure?access_token=7ef61a51358a60fe875ca4a9ab3114c06d5818c25936f51bd420a5d1e025f0ee&end=2015-04-06T23:59&nocache=1441806074364&resolution=86400&start=2015-04-05T00:00&fhir=true"
    }
  ],
  "updated": "2015-09-09T15:14:10+00:00",
  "entry": [
    {
      "subject": {
        "reference": "/api/users/1"
      },
      "resourceType": "Observation",
      "name": {
        "coding": {
          "system": "http://loinc.org",
          "code": "8480-6",
          "display": "BP sys"
        }
      },
      "valueQuantity": {
        "value": 125,
        "units": "mm Hg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      },
      "status": "final",
      "reliability": "ok",
      "appliesDateTime": "2015-04-05T14:44:00+00:00"
    },
    {
      "subject": {
        "reference": "/api/users/1"
      },
      "resourceType": "Observation",
      "name": {
        "coding": {
          "system": "http://loinc.org",
          "code": "8480-6",
          "display": "BP sys"
        }
      },
      "valueQuantity": {
        "value": 125,
        "units": "mm Hg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      },
      "status": "final",
      "reliability": "ok",
      "appliesDateTime": "2015-04-06T09:25:00+00:00"
    },
    {
      "subject": {
        "reference": "/api/users/1"
      },
      "resourceType": "Observation",
      "name": {
        "coding": {
          "system": "http://loinc.org",
          "code": "8462-4",
          "display": "BP dias"
        }
      },
      "valueQuantity": {
        "value": 78,
        "units": "mm Hg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      },
      "status": "final",
      "reliability": "ok",
      "appliesDateTime": "2015-04-05T14:44:00+00:00"
    },
    {
      "subject": {
        "reference": "/api/users/1"
      },
      "resourceType": "Observation",
      "name": {
        "coding": {
          "system": "http://loinc.org",
          "code": "8462-4",
          "display": "BP dias"
        }
      },
      "valueQuantity": {
        "value": 78,
        "units": "mm Hg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      },
      "status": "final",
      "reliability": "ok",
      "appliesDateTime": "2015-04-06T09:25:00+00:00"
    }
  ]
}

I've seen this example, but it's not very clear to me still.

Answer 1

In DSTU 2, we've brought back Observation.component so systolic and diastolic should actually be captured as components of an overall blood pressure observation. If you're using one of the intermediate versions, you'd still want to have an Observation that represented the overall blood pressure and then relationships from that observation the systolic and diastolic. That would establish the linkage.