The Language and script for the Elements of the ddexC:MessageHeader as defined in IETF RfC 4646. The default is the same as indicated for the containing composite. Language and Script are provided as lang[-scipt][-region][-variant]. This is represented in an XML schema as an XML Attribute.
A xs:string used to uniquely identify the thread of Messages of which the current Message is a part. One example of such a 'thread' is the chain of NewReleaseMessages being sent from ReleaseCreator to wholesale ReleaseDistributor 1 to retail DSP when communicating information about the same Release(s). A common MessageThreadId will allow all these messages to be tied together.