Does it distinguish a narrow and broad sense of "Valid XML document"?

I noticed there are two different ways to understand what is a "valid XML
document". 

Within normartive XML specs, the wording "valid XML document" is defined in
XML 1.0 Recommendations, in which "valid XML document" refers to (in narrow
sense) those XML documents that has a DTD and indeed conforms to the DTD.
In XML Schema recommendation, it has a similiar concept, but with a
different wording, called "schema valid instance document". 

However, in informal situations,  "valid document" usually refers to an XML
document that is conformant with a schema, either DTD or XML Schema. 

My question is if it makes sense to unify  the two concepts in certain
normative W3C document( i.e. to make "valid document" a normative term
refering to a DTD or XML Schema valid document)?



Collin