><tr><td style="white-space: nowrap">Invariants</td><td><span style="color:DarkGray"><b title="Formal Invariant Identifier">ele-1</b>: All FHIR elements must have a @value or children (hasValue() or (children().count() &gt; id.count()))</span><br/><span style="color:DarkGray"><b title="Formal Invariant Identifier">ext-1</b>: Must have either extensions or value[x], not both (extension.exists() != value.exists())</span></td></tr>
<tr><td style="white-space: nowrap"><a href="http://hl7.org/fhir/R4/profiling.