IDL43 — It is unclear where annotations can be applied

The spec says "An annotation may be applied to any IDL constructs or sub-constructs. Applying an annotation consists actually in adding the related meta-data to the element under annotation." However, there is no definition of "IDL construct" or "IDL sub-construct". Furthermore, the nonterminal <annotation_appl> does not appear on the right-hand side of any grammar rule. Thus it is not formally specified where <annotation_appl> may appear in an IDL file.