Re: Datasets and contextual/temporal semantics

On Friday, 14 October 2011, Jeremy Carroll <jeremy@topquadrant.com> wrote:
> On 10/14/2011 12:42 PM, Sandro Hawke wrote:
>>
>> TimBL used to argue that those times should be understand as Valid-Since
>> and Valid-Until times [1].  Given how they sit in the caching mechanism,
>> they are perhaps closer to transaction times, but I think Tim's point
>> was that one should try to align those sets of times anyway.
>>
>> Eventually he stopped pushing for this, when people told him that they
>> were (a) too hard to control on their web servers, and (b) they want to
>> be using them to control HTTP caching -- as intended -- not to be making
>> claims about the world.
>>
>> This is why I suggested just putting the times in the data itself,
>
> I agree with the sentiment that if dates and times of events are important
then they should be explicitly modeled. My point about these HTTP header
mechanisms is that it is basically obligatory on the web to participate in
these cache control mechanisms and a lot of the anxiety about out-of-date
data seems to me to be anxiety about our implementations that *do not check*
to see whether our local copy of someone's foaf page is or is not up-to-date
with the master copy on that person's web site, and is being misplaced as
anxiety about the underlying specification in RDF Recommendations of a
native time model.



Slight aside --- but HTML has the http-equiv construct, eg
http://www.w3.org/TR/html5/semantics.html#pragma-directives

While this was no good regarding Http-range14 since even serving up such an
HTML doc via HTTP 200 means it's too late by time we've got the doc to use
http-equiv HTML meta to issue different http headers. However, maybe here we
could use in-HTML metadata to express header info, for the cases where real
http headers can't be changed?

Dan

> Jeremy
>
>