Label descriptor by Label element

The Label element is used to provide a textual description of a preselection when further details need to be signaled. The text for the label is inserted between the start tag and the end tag of the Label element.

The optional attribute lang signals the language of the provided label. By using multiple label elements with different lang attributes, it is possible to signal the label content in different languages.

If the AC4PresentationLabelBox is used inside the AC4SampleEntryBox, the Label element with the referencing Preselection element should match the corresponding presentation_label.