Feeds by date

[Janne Jalkanen <Janne.Jalkanen@xxxxxxxxx>]

If your computer is off for two weeks, and you restart it - you might be 
missing some entries from the blogs you are following, just simply 
because the Atom feed contains only the 20 latest items.

The other thing is that even if there has been only a single addition 
since your last fetch, you will essentially be downloading redundant 
content.  Which is not good for mobiles.

How about using something like ETags or If-Modified-Since to support 
dynamic generation of feeds?  I know dynamic generation is a big burden 
on many devices, and you really want to have a static file to serve, but 
in some situations it might come in handy.

It should actually be pretty transparent, and the support should be 
optional.  If the request look something like

GET /atom.xml HTTP/1.1
ETag: 2004-05-13T15:32:08Z

The server would then be free to serve only content changed since the 
tag date, or just the 20 last items or so.  In fact, since most 
aggregators hit a site every hour, it is conceivable that a smart server 
would keep a separate atom file with just the items from the last two 
hours, and serve that in case the date matches and there has been new 
content.  In those rare cases, where someone asks the feed after two 
weeks of silence, it's okay to regenerate it for them.

But if the server does not support dynamic generation, no worries.  
It'll just use the ETag to see whether it should serve a 301 
NOT_MODIFIED or the entire feed...

Any comments?

/Janne, thinking again about the pesky bandwidth thing...