In OData we can annotate model data, we can annotated instance data, and we can annotated vocabularies. But currently it's not possible to use a Vocabulary term to annotate an annotation. The following is invalid:

<Record Type="UI.DataField">
<PropertyValue Property="Label" String="A Picture!" />
<PropertyValue Property="Value" Path="Product/ImageOfProduct" >
<Annotation Term="UI.IsImageURL"/>
<Annotation Term="UI.HighResolution"/>
</PropertyValue>
</Record>

We want to use the edm:Annotation element as a child of the dynamic expressions edm:PropertyValue, edm:Record, and edm:Collection.