Re: [apps-discuss] HTTP header field for "URI lifetime"

Herbert Van de Sompel <hvdsomp@gmail.com> Wed, 20 May 2015 14:42 UTC

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References: <555C284E.1030208@berkeley.edu> <0AD556BB-614D-47D0-8509-C8670E01E82B@mnot.net> <555C46AD.2080006@berkeley.edu>
Date: Wed, 20 May 2015 08:42:39 -0600
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From: Herbert Van de Sompel <hvdsomp@gmail.com>
To: Erik Wilde <dret@berkeley.edu>
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Cc: Mark Nottingham <mnot@mnot.net>, Herbert Van de Sompel <hvdsomp@gmail.com>, IETF Apps Discuss <apps-discuss@ietf.org>
Subject: Re: [apps-discuss] HTTP header field for "URI lifetime"
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hi,

(Thanks for cc-ing me)

Rather interesting. Indeed, it is not directly related to Memento; the
Memento-Datetime header is for expressing that a resource has been
"frozen" at the datetime that is conveyed as the header value, i.e. it
entails a promise that the resource will not change beyond the
expressed datetime. The way I understand what you are discussing, this
is about a header that indicates that a URI will no longer be existent
starting at a certain date, ie past that date one can expect a 404 or
similar bad news.

But there is a relation with a possible web archiving use case: if a
web archiving client comes across a URI-R that indicates its
extinction datetime, then the client could make it a priority to crawl
that URI-R and archive its representation at URI-M in a web archive.
Using Memento, URI-M would then have a HTTP link with relation type
"original" pointing at URI-R. Even when URI-R is gone, using Memento,
URI-R could still be used to access archived snapshots of URI-R such
as URI-M. Magic :-)

I am thinking that this could be particularly useful for shortened
URIs, many of which - as we know - aren't long lasting and the minters
of those URIs are very much aware of that. If these minters would
convey their short term URI retention strategy using a header, then
applications that consume/mine tweets and resources linked in tweets
(there's a lot of research in this realm) could optimize their data
collecting strategy by taking the URI expiration date into account.

Cheers

Herbert

On Wed, May 20, 2015 at 2:32 AM, Erik Wilde <dret@berkeley.edu> wrote:
> hello mark.
>
> On 2015-05-20 08:50, Mark Nottingham wrote:
>>
>> On 20 May 2015, at 4:23 pm, Erik Wilde <dret@berkeley.edu> wrote:
>>>
>>> we had some discussions at www2015 about a possible HTTP header for
>>> exposing a URI's "lifetime". please do not get hung up on any terminology,
>>> but the scenarios we discussed included:
>>
>> Hm. It's come up before, and there's a legitimate distinction between this
>> (which is about the resource) and Expires (which is about a specific
>> representation).
>
>
> we were specifically not interested in the caching mechanisms, because like
> you say, these are about the "lifetime of the resource state", and not about
> the resource as such.
>
>> However, I'm having trouble seeing how it would be useful to clients — can
>> you illustrate the use cases a little more fully?
>
>
> so, one thing from my own experience is retention in content management:
> there are many scenarios where some data needs to be kept around for
> regulatory reasons for a certain period of time, and then it can and maybe
> will be removed. that's a fairly large category of scenarios.
>
> another one was decommissioning of services: at some point, a decision may
> be made to take down a service at some point in time. if this could be made
> visible in the uniform interface, then clients having awareness of this
> would have an easier time to maybe alert users. for some time, these
> services may still operate but redirect, and that at some time they may
> disappear completely.
>
>> What will a client do with that information?
>
>
> that depends on the client. services might simply raise alarms that some of
> the resources they are using are about to disappear. clients such as
> browsers may alert users that bookmarks are going to expire and encourage
> users to maybe check for redirects, or archive the page before it
> disappears.
>
>> Given that this necessarily requires someone to predict the future and
>> make some level of commitment to that, it may be that the information it
>> conveys is of very limited use — i.e., people won't trust it :)
>
>
> retention and decommissioning are relatively reliable ways to predict the
> future, but of course in many other cases there is no such mechanism. and of
> course this is more a hint than anything else, but it may be a hint worth
> having in the uniform interface.
>
>>> - a service doing archiving and wanting to expose that resources will
>>> only be kept until a certain time, and then disposed.
>>
>> This seems somewhat related to Memento; CC:ing Herbert for his comment /
>> information.
>
>
> yes, we did talk about memento. this just seemed to be way more than what we
> were discussing, and mostly revolve around the scenario of how to expose
> archived information ("looking into the past"), and not so much about just
> looking, as you said it, "into the future",
>
> thanks and cheers,
>
>
> dret.
>
> --
> erik wilde | mailto:dret@berkeley.edu  -  tel:+1-510-2061079 |
>            | UC Berkeley  -  School of Information (ISchool) |
>            | http://dret.net/netdret http://twitter.com/dret |



-- 
Herbert Van de Sompel
Digital Library Research & Prototyping
Los Alamos National Laboratory, Research Library
http://public.lanl.gov/herbertv/

==