QualifiedName values shall be encoded as a JSON string using the format defined in 5.1.12 however, the form with the NamespaceIndex is not allowed.

When decoders need to replace a NamespaceUri with a NamespaceIndex and the NamespaceUri cannot be mapped to a NamespaceIndex, then decoders shall use 0 for the NamespaceIndex and the JSON string as the Name.