PREFIX : <http://hl7.org/fhir/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
BASE <http://schema.example/>

start = @<ObservationShape>

<ObservationShape> {               # An Observation has:
  :status ["preliminary" "final"]; #   status in this value set
  :subject @<PatientShape>         #   a subject matching <PatientShape>.
}

<PatientShape> {                   # A Patient has:
 :name xsd:string*;                #   one or more names
 :birthdate xsd:date?              #   and an optional birthdate.
}