On 2015-10-28 02:12, Paul Eggert wrote:
lester@lsces.co.uk wrote:
The version number is essential data
It's not essential to put the version number into zic's output, as the tz project has been operating successfully for decades without doing so. Although there are benefits to having a version number in the data, there are costs too, and it's not clear which is greater. If one needs a unique number to briefly identify a data file, one can use a hash function of the data. This should suffice for tzdist's needs, so that tzdist shouldn't require a version number in the data.
Seems essential to document the provenance of the data using the kind of output --version produces from some packages, which include explicit build libraries and versions, e.g. 2015g+zone1970.tab where zone.tab could replace zone1970.tab; +backzone, and +(NIST)leap-seconds.3629404800 could be added, with (IERS) a (singular but possibly more secure and authoritative) alternative to (NIST); and local commit hash added like +https://github.com/eggert/tz/commit/6bf2f29c6458f8aa245dd5780235a38e6142bbef. [Last time I checked, only 9 of 24 NIST servers, and 2 of 9 nist.gov servers {time,wwv} offered anonymous FTP leap seconds files.] -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada