impl xs opti w3c dom DOMException w3c dom DOMImplementation w3c dom w3c dom DocumentType schemadomimplementation domimplementation schemadomimplementation singleton schemadomimplementation domimplementation getdomimplementation singleton schemadomimplementation createdocument namespaceuri qualifiedname documenttype doctype domexception domexception domexception.not_supported_err documenttype createdocumenttype qualifiedname publicid systemid domexception domexception domexception.not_supported_err getfeature feature version singleton.hasfeature feature version singleton hasfeature feature version anyversion version version.length feature.equalsignorecase feature.equalsignorecase anyversion version.equals version.equals version.equals