Service Name is a string label that uniquely identifies each service within the domain. Public Identifier datatype is the public identifier by which an instance of a Business Entity can be identified. It's called Public Form Identiier rather then Content Form Identifier for historic reasons as a result of confusion over definitions of terms. Public Form Identifier datatype is the public identifier by which an instance of a Content Form can be identified. It's called Public Form Identiier rather then Content Form Identifier for historic reasons as a result of confusion over definitions of terms. The standard Identifying Block for all messages.