[tz] An alternate framing of timezone maintenance

Russ Allbery eagle at eyrie.org
Wed Sep 22 23:14:26 UTC 2021

Stephen Colebourne via tz <tz at iana.org> writes:

> In response, I'll say that I don't believe that naming is the root of
> the problem. There has been a lot of distracting discussion around ISO
> countries, city names and more, but the fundamental issue actually is
> with the timekeeping data set, not the naming. Whatever a region is
> called, it still represents *somewhere*. Changing the history of that
> somewhere is a big deal, whatever name you give the region.

I think you have not understood the post to which you are replying.

Your objection that started this recent discussion is solely contained in
the naming layer.  You are objecting to the change to where Europe/Oslo
points (and similar changes).  Viewed through the separation of the
timekeeping data set and the naming layer, your objection is that
Europe/Oslo used to point to TZ1386 (or whatever), which contains
historical data (of whatever quality) for Oslo, and now points to TZ1490
(or whatever), which contains historical data for Berlin.

Nothing has changed about the rulesets.  Nothing has changed about the
recorded history.  What has changed is where the *name* Europe/Oslo
points, since it becomes an alias to Europe/Berlin instead of pointing to
a separate ruleset (which still exists).

Your concern can therefore be completely addressed in the naming layer by
pointing the name Europe/Oslo back at TZ1386.

All of the various build options that incorporate backzone or portions of
backzone are, in this model, accomplishing two things: choosing which data
sets to build (so, for instance, whether to build the TZ1386 ruleset at
all), and modifying the many-to-one mapping between the naming layer and
the timekeeping data set.  The stability that you are asking for is
addressed in this model by (a) always building the backzone rulesets so
that their permanent identifiers are available, and (b) maintaining the
mapping from Europe/Oslo to that identifier.

The point of my message is that focusing on the effects that you see is
misleading because the nature of the data is not what one might think it
is when one is only looking at the downstream effects.  You seem to think
that the data has changed, but the data has not.  Only the names assigned
to it have changed.

> Don't get me wrong, I do understand the attraction of arbitrary names.
> But the existing names will never disappear as they are so widely used,
> and so useful.

Oddly, that was exactly the point I was making in the message to which
this theoretically was a reply.

Russ Allbery (eagle at eyrie.org)             <https://www.eyrie.org/~eagle/>

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