The constants +rdf-...+ and +rdfs-...+ are now DEFVARs. Clozure CL
highlighted an issue with the serialization of URI objects.  It
appeared to be compliant with the standard, and that there wasn't any
very feasible workaround that kept the values as DEFCONSTANTs.  They
still have the same names (surrounded by +'s) and should not be