[DOMCore] is an empty namespace always equal to a null namespace?

The setAttributeNS() algorithm explicitly includes the following step:

> If namespace is the empty string, let namespace be null. 

getAttributeNS, hasAttributeNS and removeAttributeNS do not include this 
step, and, as the spec is currently written, I think they would treat "" 
differently than null.  Is that an error in the spec?

     David