<Substance xmlns="http://hl7.org/fhir"><id value="f203"/><identifier><system value="http://acme.org/identifiers/substances"/><value value="1234"/></identifier><category><coding><system value="http://terminology.hl7.org/CodeSystem/substance-category"/><code value="chemical"/><display value="Chemical"/></coding></category><code><concept><coding><system value="http://snomed.info/sct"/><code value="88480006"/><display value="Potassium"/></coding></concept></code></Substance>