As I see it, TEI is for describing the elements of a document; transforming to HTML with RDFa can add a meaningful interpretative layer, stating what the document is saying about the external world.
T. Nellhaus. 1, page 257-277. (2001)"It is unclear, however, what relationship there might be between TEI headers and RDF. In principle, it should be feasible to create a crosswalk...".