RE: Global concept identification and reference

I have a question related to the points raised by Andrew Houghton and Aida 
Slavic. In fact this is (I think) an extension of the question Aida asked.

Organizations adopting a widely-used thesaurus, like the OECD 
Macrothesarus, nearly always make some changes to it so that it meets local 
needs. They have bought the thesaurus or obtained it legally, and as long 
as the changes are not massive, copyright has never to my knowledge  been 
an issue in this regard: they are not re-publishing the thesaurus, just 
using it in their application. They state publicly that they use the 
original thesaurus (say the Macrothesaurus), though they will likely 
provide a human-readable note to a user saying what has been changed for 
the local application.

If now, however, in a semantic web environment, they need to expose their 
concepts with an identifier, what identifier do they use for the new or 
modified concepts they have introduced, and for the old ones that they have 
taken over?

a)  Should they use an identifier that identifies the original thesaurus as 
the source for _all_ concepts, even though strictly speaking this isn't 
true, and an application relying on the fact that they do may be in for 
some surprises?
b) Do they create a new identifier for their "version" of the thesaurus and 
use this even for concepts which are the same in the local version as they 
are in the standard version?
c) Do they use an identifier to the original thesaurus for the terms that 
have not changed and use an identifier for their local version for the 
terms that have been modified or added? If so, how does an application 
discover what the local modifications are?

In an SKOS environment, would they do the same whether they are using an 
'official' URI or the indirect method of reference?

Thanks,

Ron
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Ron Davies
Information and documentation systems consultant
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