Currently, specifying the annotation and the real value to property is a bit complicated:
<textbox value="@annot()">
<attribute name="value">the real value</attribute>
</texbox>

New Feature Request:
It can be simplified by introducing a namespace as follows:
<textbox value="the real value" a:annot="@annot()" xmlns:a="annotation"/>

Furthermore, if a user want to specify a value that looks like an annotation, he could do:
<textbox z:value="@annot()" xmlns:z="zul"/>

since a non-annotation namespace is specified explicitly, so the value is considered as a real value rather than annotation.

On the other hand, if the attribute is not specified with any annotation, whether it is an annotation is detected automatically (as the current spec does).