[r-t] Extension question

[Mark Davies]

Don writes,

> Is there any reason, other than side effect of the classification scheme,
> for this, or is it just arbitrary?

I really don't know, since I didn't design the extension scheme, but I'm 
guessing it's just a side effect which no-one has thought about before, 
and also hasn't yet come up in practice. I stand to be corrected!

MBD

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