Hi,XBRL (which is based on XML) is an interesting example for the way namespaces and QNames are handled. Technically, everything in there (concepts, units, types) is a QName, however there is a very widespread convention to stick to the same prefix binding at least within a regulatory authority. That way, one can rely on the prefix and local name, does not need to resolve to long names *even dynamically*, and one can optimize accordingly both in space and time.This convention is actually made explicit by several authorities such as the SEC in terms of recommended prefix usage, and a recent working draft in the XBRL specification family formalizes this approach as SQNames (= what Roger calls abbreviated QNames).Of course, it may not scale up as far as URI namespaces because you lose the "using a domain you own"-perk of URIs to avoid collisions, but so far it works pretty well because the number of namespaces is still reasonable at the scales considered.Kind regards,Ghislain