In particular, section 3. "Transporting RDF" mentions "embedding" (this
seems to mean an element reference), "along-with" (external markup), service
bureau" (external markup) and "wrapping" as the four ways of associating
descriptions and resources. But the current spec only considers wrapping. I
guess this is because these other parts of RDF rely on X-Link. (Embedding
and external markup could be done using ISO Topic Navigation Maps.)
Rick Jelliffe