Entities from source doctype?

Greetings,

Can I fetch an entity value that's defined in the doctype portion of a
source document, but not used by name anywhere else in the source
document?

For example, say the source xml document looks something like this:

<!DOCTYPE mydoctype [
<!ENTITY mynote  "this is a special note" >
]>
<mydoctype>
       <specialnote/>
</mydoctype>


I can't use the unparsed-entity-uri function, because I don't know the
name of the entity: It's never used by name. Instead, if I come across
the 'specialnote" element, I want to substitute the value stored in
the 'mynote' entity.

Can I fetch the value of the "mynote" entity or must it be used (or
name known) in order to access it?