[tz] Rules for TZ+ database

[Stephen Colebourne]

On 5 September 2013 13:55, Paul Eggert <eggert at cs.ucla.edu> wrote:
> We would like to allow zones to be added even if they exceed
> the current guideline.  These zones are currently out of
> scope, and most users won't want them (as they'll be
> presented with unnecessary choices when selecting TZs, which
> makes their jobs harder), but a few will want them and if
> the data are high quality I don't see any reason to exclude
> from the database.  It's just that we need a mechanism for
> winnowing out these extra zones, as I expect we don't want
> them installed by default on POSIX platforms.  Zefram has
> proposed one mechanism, we're currently evaluating it, and I
> hope and expect that it or something like it will appear in
> the tz database soon.  Once that happens, we'll have the
> mechanism we need, and a place for these new zones.

Its important not to forget the existence of non zic parsers here.
Adding lots of new data to the current set of files would impact them,
forcing them to use all the new IDs or implement their own winnowing.

Whereas if the additional zones were placed in a new file "extended",
then zic and non-zic consumers could easily choose whether to include
the extra data or not.

None of the above should stop existing Zone and Link entries from
being expanded with researched historic data. ie. pre-1970 data for
the existing set of IDs should remain in the main files, unless an
entirely new data format is being created (which I'm not enthused
about).

Stephen