creation of CSSStyleDeclaration objects

I can't find any mention in PR-DOM-Level-2-Style-20000927 of how
CSSStyleDeclaration objects will be created. Should I assume that it will
simply be a matter of invoking a constructor of an implementation class that
implements CSSStyleDeclaration? My first guess was that CSSStyleSheet would
provide a createCSSStyleDeclaration method but that is not the case.