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

[Paul Eggert <[e-mail]>]

Cyrus Daboo wrote:
> ETag is something very specific to the HTTP protocol and is used in several
> ways - in particular it is important for caching by intermediaries etc.

Yes, and that's an argument for our using ETag instead of an 
application-specific versioning system.  Why reinvent a caching system when we 
can use HTTP's?

 > Plus
> there are reasons when you might want to refresh the client data in the absence
> of a publisher version upgrade (e.g., the tzdist server is using a more
> efficient, compact representation that it previously had).

That sounds fairly unusual, but if it happens, then the server could append 
something to the ETag, e.g., "tz2014j-format2" instead of plain "tz-2014j". 
That is, the ETag needn't be just the publisher version; it could be the 
publisher version plus the server format if the latter matters.

> HTTP has the concept of "strong" and "weak" ETags (see
> <http://tools.ietf.org/html/rfc7232#section-2.1>). It may be possible to make
> use of "weak" ETags for the version id.

Sure, and if people want to use weak ETags then they wouldn't need to mess with 
"-format2" suffixes.