[whatwg] Proposal: add attributes etags & last-modified to <link> element.

[Philipp Serafin]

 On 21.09.2010 21:01, Aryeh Gregor wrote:
> On Mon, Sep 20, 2010 at 2:25 AM, Julian Reschke <julian.reschke at gmx.de> wrote:
>> Resources that should be cached (stylesheets, images) but change at
>> unexpected times are indeed a problem.
>>
>> A well understood approach is to push some kind of version indicator into
>> the URI (such as query parameter).
> This is usually workable in my experience, I agree, and I'd be
> interested to know of use-cases where it's not close to optimal. i
One disadvantage I think the version-in-URI approach has is that it's
completely transparent to the HTTP caching system. In particular, it
doesn't give caches any information about when a resource is expired.
This isn't really an issue if you really know for sure that your
resource in question only changes very rarely. However if you have a
resource that you would like to cache but where you cannot reliably
predict how fast it will change, this might become a problem. If your
resource changes too fast, this will clog up caches with dozens of old
versions which cannot be deleted because of their long-lived expiry
header. (Concrete example: Consider the avatar images of an internet
message board. Most users only set their avatar once when they register,
though a few may change them based on mood, holidays, etc.)

Regards,
Philipp Serafin