This is the Continuous Integration Build of FHIR (will be incorrect/inconsistent at times). 
See the Directory of published versions
How 'Basic' can be used for essoteric resources - in this case, a UML class model
{
  "resourceType" : "Basic",
  "id" : "classModel",
  "text" : {
    "status" : "generated",
    "div" : "<div xmlns=\"http://www.w3.org/1999/xhtml\">\n      <p><b>Class1</b></p>\n      <ul>\n        <li>Attribute1: 1..*</li>\n        <li>Attribute2: 0..1</li>\n      </ul>\n    </div>"
  },
  "extension" : [{
    "url" : "http://example.org/do-not-use/fhir-extensions/UMLclass",
    "extension" : [{
      "url" : "name",
      "valueString" : "Class1"
    },
    {
      "url" : "attribute",
      "extension" : [{
        "url" : "name",
        "valueString" : "attribute1"
      },
      {
        "url" : "minOccurs",
        "valueInteger" : 1
      },
      {
        "url" : "maxOccurs",
        "valueCode" : "*"
      }]
    },
    {
      "url" : "attribute",
      "extension" : [{
        "url" : "name",
        "valueString" : "attribute2"
      },
      {
        "url" : "minOccurs",
        "valueInteger" : 0
      },
      {
        "url" : "maxOccurs",
        "valueInteger" : 1
      }]
    }]
  }],
  "code" : {
    "coding" : [{
      "system" : "http://example.org/do-not-use/fhir-codes#resourceTypes",
      "code" : "UMLCLASSMODEL"
    }]
  }
}
 
Usage note: every effort has been made to ensure that the
examples are correct and useful, but they are not a normative part 
of the specification.