where are the domain/range for "domain"/"range" defined?

I couldn't find anywhere in the RDF schema for RDF schemas where the domain
and range for the "domain" and "range" properties are specified. Is there a
reason why they couldn't be? (Presumably the domain of both is "Property"
and the range of both is "Class".)

My research team at Bowstreet is building a web-based schema-driven RDF
editor and just got tripped up by this.

Thanks

James
--
James Tauber
jtauber@bowstreet.com
Director XML Technology
Bowstreet www.bowstreet.com