How 'basic' can be used for future resources - in this case referral (id = "referral")

<?xml version="1.0" encoding="UTF-8"?>

<!--   This is a bare-bones referral intended to show how the Basic resource might be
 used.
A real referral would likely include references to supporting information such
 as medication lists,
problem lists, allergy lists, etc.
Note: ServiceRequest has been incorporated in the specification; this example will
 be rewritten
in a future version (todo).
  --><Basic xmlns="http://hl7.org/fhir">
  <id value="referral"/> 
  <text> 
    <status value="generated"/> <div xmlns="http://www.w3.org/1999/xhtml">
      <p> <b> Patient:</b> Roel</p> 
      <p> <b> Requestor:</b> Dokter Bronsig</p> 
      <p> <b> Type:</b> Consultation</p> 
      <p> <b> Target Date:</b> April 1 - April 31</p> 
      <p> COMPLETED</p> 
      <b> The patient had fever peaks over the last couple of days. He is worried about these
         peaks.</b> 
    </div> 
  </text> 
  <extension url="http://example.org/do-not-use/fhir-extensions/referral#requestingPractitioner">
    <valueReference> 
      <reference value="Practitioner/f201"/> 
      <display value="Dokter Bronsig"/> 
    </valueReference> 
  </extension> 
  <extension url="http://example.org/do-not-use/fhir-extensions/referral#notes">
    <valueString value="The patient had fever peaks over the last couple of days. He is worried about these
     peaks."/> 
  </extension> 
  <extension url="http://example.org/do-not-use/fhir-extensions/referral#fulfillingEncounter">
    <valueReference> 
      <reference value="Encounter/f201"/> 
    </valueReference> 
  </extension> 
  <modifierExtension url="http://example.org/do-not-use/fhir-extensions/referral#referredForService">
    <valueCodeableConcept> 
      <coding> 
        <system value="http://snomed.info/sct"/> 
        <code value="11429006"/> 
        <display value="Consultation"/> 
      </coding> 
    </valueCodeableConcept> 
  </modifierExtension> 
  <modifierExtension url="http://example.org/do-not-use/fhir-extensions/referral#targetDate">
    <valuePeriod> 
      <start value="2013-04-01"/> 
      <end value="2013-04-15"/> 
    </valuePeriod> 
  </modifierExtension> 
  <modifierExtension url="http://example.org/do-not-use/fhir-extensions/referral#status">
    <valueCode value="complete"/> 
  </modifierExtension> 
  <identifier> 
    <system value="http://goodhealth.org/basic/identifiers"/> 
    <value value="19283746"/> 
  </identifier> 
  <code> 
    <coding> 
      <system value="http://terminology.hl7.org/CodeSystem/basic-resource-type"/> 
      <code value="referral"/> 
    </coding> 
  </code> 
  <subject> 
    <reference value="Patient/f201"/> 
    <display value="Roel"/> 
  </subject> 
  <created value="2013-05-14"/> 
  <author> 
    <reference value="Practitioner/example"/> 
  </author> 
</Basic>