The taxon concept schema has no enumerated list of ranks. I believe this will be a major interoperability block, since although latin rank names are "standard" a strong tendency exists to use local name like kingdom = Reich, etc.
In UBIF I am proposing a rank enumeration. This has been substructured into rank blocks which are joined by a union in TaxonomicRankEum?. I would appreciate any comments whether this could - perhaps in parallel or as a recommended alternative - be used as a common vocabulary. Note that among the UBIF values, I tend to accept aggr as a pseudorank, but think spgroup is a redundant synonym. Please see on the UBIF wiki 
http://efgblade.cs.umb.edu/twiki/bin/view/UBIF/TaxonomicRankEum
Would it make sense to use this enumeration in the Taxon Concept schema?
Gregor Hagedorn -- 12. Aug. 2004
An enumerated list would seem to make sense, especially for the language issues you raise. I think we did not enumerate it because we were concerned about capturing all of these nonstandard ranks that you allude to, but we dont sufficiently understand.
ABCD too has an enumeration of HigherTaxonRankType for ranks above genus. How do they relate to UBIF proposals?
We would suggest that if people want an enumeration for this or another value they start a list of values somewhere on the WIKI that people can consider, and give their opinions on the values and whether an enumeration is a good idea. Alternatively if people are happy with the list on Gregor's wiki or as implemented in the UBIF Type Library we could all use that.....TrevorPaterson 12 Aug