Lester Caine wrote:
My reading of the paperwork so far is that it is planned to have a full range base,
Sorry, I don't know what a 'full range base' is, but there are no plans for a full coverage of all civil time stamps in every era. My only plan for backzone now is to be a repository for questionable/out-of-scope (pre-1970) data that we can easily move out of the tz database proper, one step at a time. If people want to donate other data (within reason; see below) that'd be fine, but it's not something I want to spend time on. The backzone file is out of scope for this project and if managing it becomes a significant burden we should spin it out into a separate project.
what is not clear is how new historic data that identifies that a current timezone now has two historic routes.
For current backzone entries this can be deduced from pre1970.tab. If backzone gets more complicated I suggest adding commentary to it in case a zone's boundaries are not clear. Or if that's not enough, do a database redesign as a separate project.
The planing seems to be based on tz zones, but as with all of these things there is no planning to manage tz identifiers.
The current approach will not scale. It's meant only for relatively modest growth, where we can manage identifiers the same way we've always managed them. Sorry, but a database redesign will be needed to cover appreciable quantities of pre-1970 data.
Can we not just describe 'backzone' as historic data.
Sorry, I don't follow. The tz database is almost all historic data.
That the provenance of some material is 'poorly-sourced' just needs to be properly flagged within the file.
It is, in commentary within the file. If those comments are not clear please feel free to submit patches; see the CONTRIBUTING file.