{"resourceType":"SearchParameter","id":"example-extension","url":"http://hl7.org/fhir/SearchParameter/example-extension","name":"Example Search Parameter on an extension","status":"draft","experimental":true,"publisher":"Health Level Seven International (FHIR Infrastructure)","contact":[{"telecom":[{"system":"url","value":"http://hl7.org/fhir"}]}],"description":"Search by url for a participation agreement, which is stored in a DocumentReference","code":"part-agree","base":["Patient"],"type":"reference","expression":"DocumentReference.extension('http://example.org/fhir/StructureDefinition/participation-agreement')","xpath":"f:DocumentReference/f:extension[@url='http://example.org/fhir/StructureDefinition/participation-agreement']","xpathUsage":"normal","target":["DocumentReference"]}