Danny Ayers on relational, xml and RDF databases:
“Traditional relational databases work best with table-shaped data. XML databases work best with tree-shaped data. RDF databases work best with graph-shaped data. The Web consists of graph-shaped data.”
XML data is already being mapped to relational (Microsoft and Oracle efforts). Similar efforts exist in the case of RDF to relational mapping. It looks as if as we move more into XML and RDF based applications, we need a strategy for the co-existence and ways to semantically link fragments of these different databases.