Re: [Tzdist] Fwd: [tzdist] #32 (service): managing historical data

[Lester Caine <[e-mail]>]

On 10/12/14 15:39, Cyrus Daboo wrote:
> Today one might need to pray, but once tzdist is deployed and in use the
> goal is that users can rely on the data they have to be up to date and
> accurate (just as much as one can rely on an NTP server to give your
> device the correct time, or rely on the user having set the correct
> local time zone for the device etc).

This STILL misses the race hazard that exists with CURRENT data! First
it assumes that everybody s using the one published set of data. That
has been thrown out, so several sets will exist. Once one looks at a new
event diary one also has to establish just which publisher it is using!
One then gets the 'current' data for that publisher, but if the diary
was published today, and there has since been a change of data, then
what was used by the diary is out of sync.

OK one way of making your system work is to INSIST that ever published
dairy is always updated to the current data set for their publisher? Not
going to work, it takes time to find that what was published now needs
updating, and the material published may well already be cached around
the network, so an update will take time to propagate.

Historic material archived today will tag the publisher and the version,
and as long as in 10 years time the matching data can be recovered there
is not a problem. But the same simple process provides the necessary
security to CURRENT material since 'latest' may well not be the version
used five minutes ago ...

-- 
Lester Caine - G8HFL
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