gistfile1.as

public class Order
{
    [ChoiceType("Book")]
    public var books:Array;
}

public class Book
{
    [Required]
    public var isbn:String;
    
    [Required]
    public var title:String;
    
    [Required]
    public var author:String;
    
    public var comment:String;
    
    [TextNode]
    public var description:String;
}