There is a DefaultProperty annotation in FXML which is used to help specify which property (typically a collection property I would venture to guess) should be considered the "default" property, such that in FXML you can say:

<Parent>
    <Child/>
    <Child/>
</Parent>

instead of

<Parent>
    <children>
        <Child />
        <Child />
     </children>
</Parent>

So we will want to use @DefaultProperty in a lot of places in the runtime libraries, but we'd like to keep FXML separate as far as dependencies go. We could move the annotation to the beans package.