[DOMCore] createElement() and HTML-specific element interfaces

I can't see anything in the DOMCore spec that references the fact that 
HTML defines lots of Element subclasses and that createElement('table'), 
for example, is supposed to return an instance of HTMLTableElement.

Also, it is unclear to me what should happen if d is a document returned 
by createDocument (not createHTMLDocument) and I call 
d.createElement("table").  The spec is clear that the element will use 
the HTML namespace, but it is not clear whether the resulting object is 
instanceof  HTMLTableElement or just Element.

createElementNS() is similarly underspecified: under what circumstances 
does it create instances of the HTML-specific interfaces defined in the 
HTML spec?

     David