Multiple preferred values [was: Add retired tag "eml" to the IANA registry]
doug at ewellic.org
Mon Dec 14 14:49:49 CET 2009
"Michael(tm) Smith" <mike at w3 dot org> wrote:
> If it's anticipated that there's any possibility in the future of tags
> being split, it would seem like there might be a need to have a means
> to specify multiple preferred values.
Randy said that "BCP 47... doesn't allow splitting a tag," but I think
what Michael means here, and how many people will interpret the actions
of ISO 639-3/RA and their effects on the Registry, is that when the RA
retires code element 'eml' and creates 'egl' and 'rgn', that has the
practical effect of "splitting" 'eml' into 'egl' and 'rgn'. That is
something which we can expect to happen many more times, and which was
anticipated in the development of RFC 5646.
The Preferred-Value field is provided to allow automatic one-to-one
mapping. An example is that, because ISO withdrew 'iw' for Hebrew in
favor of 'he' some 20 years ago, the Registry entry for 'iw' has a
Preferred-Value of 'he' to assist matching and automatic retagging.
If you provide multiple Preferred-Values, you really haven't solved the
problem in the way you might think: should a given piece of text marked
'eml' match a search for 'egl', or not? Since there is no reliable way
to answer this question automatically, a human-readable Comments field
turns out to be a better solution. See the region subtag 'CS' to see
how this sort of multiple-split problem has been handled in the past.
Doug Ewell | Thornton, Colorado, USA | http://www.ewellic.org
RFC 5645, 4645, UTN #14 | ietf-languages @ http://is.gd/2kf0s
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