TDWG-SDD folk:
One more thought which I should have mentioned, the SEEK project is working with GBIF through Jesse Kennedy's Napier University lab on a SEEK concept schema with the objective supporting concept-based databases, IR of concepts and other fun stuff such as web-based services for concept identification, resolution and disambiguation. I believe Jessie plans to present that schema at the TDWG meeting this year.
I guess the logical end point of my argument would be that the two standards might become one, so that taxonomic concepts could be used by both groups of scientists from a single schema.
It seems inevitable that GBIF, SEEK, Berlin, or whomever will put together a satisfactory, implementable, concept schema within the next year or two. My only thought is that the SDD standard might, with what seems to be a pretty minor shift in organization, be part of the broader concept effort.
Excuse, if you all have been through this discussion N times!
Jim B.