A separate layer for semantics is a really excellent idea; something like "cascading semantics sheets"* -- instead of cluttering your markup with tons of extra

A separate layer for semantics is a really excellent idea; something like "cascading semantics sheets"* -- instead of cluttering your markup with tons of extra semantic information, frequently duplicated, just use existing CLASS and ID and attributes, plus CSS selectors, to specify elements and define roles for them within the linked document. Thus if the browser understands this extra semantic information it can use it efficiently, and if it doesn't then you've not made your markup crazily crowded for no reason. * except those would also be CSS, so maybe "cascading semantics documents", or CSD