[tz] Proposed patch - Theory notes for backward file

[Stephen Colebourne]

On 5 September 2013 15:15, Zefram <zefram at fysh.org> wrote:
> Stephen Colebourne wrote:
>>My primary concern is ensuring that the backward file is removable -
>>ie. no other files contain the "inactive" backward Link entries.
>
> These statements don't match.  For the "backward" file to be removable
> what you need is that the "backward" file does not contain any "active"
> entries.  No other files containing "inactive" entries is what's needed
> to have an easy way of feeding only "active" entries to zic.  Maybe you
> want both of these things?
>
> I'd also like to see the active and inactive links distinguished somehow,
> for internal clarity.  I'm not so concerned about the mechanism by which
> they're distinguished, but segregating them fully by file certainly has
> its attractions.  FWIW, my winnowing branch effectively distinguishes
> between active and inactive links for geographical zones by whether it
> includes population data.  (It doesn't thus distinguish active/inactive
> non-geographical zones.)

The backward file contains this line for example:
 Link Asia/Kolkata Asia/Calcutta

I'm simply arguing that the Asia/Calcutta ID should only appear in
backward, with Asia/Kolkata being used everywhere else.
That way, excluding the backward file has no effect other than
removing "no longer desirable" IDs.
Stephen