Enclosing element to compartmentalize UI specifications.

• BillboardAction (min: 0, max: unbounded): Billboard table item with child Controls
• Binary (min: 0, max: unbounded)
• ComboBox (min: 0, max: unbounded): ComboBox table with ListItem children
• Dialog (min: 0, max: unbounded): Dialog specification, called from Sequence
• DialogRef (min: 0, max: unbounded): Reference to a Dialog specification.
• Error (min: 0, max: unbounded): Error text associated with install error
• ListBox (min: 0, max: unbounded): ListBox table with ListItem children
• ListView (min: 0, max: unbounded): ListView table with ListItem children
• ProgressText (min: 0, max: unbounded): ActionText entry associated with an action
• Property (min: 0, max: unbounded)
• RadioButtonGroup (min: 0, max: unbounded): RadioButton table with RadioButton children
• TextStyle (min: 0, max: unbounded): TextStyle entry for use in control text
• UIText (min: 0, max: unbounded): values for UIText property, not installer Property
• Sequence (min: 1, max: 1)
  1. AdminUISequence (min: 0, max: 1)
  2. InstallUISequence (min: 0, max: 1)