Re: Protocols/APIs and redirects

Dear all,

I hope that it's useful to share our experiences with redirects in the
Memento "Time Travel for the Web" project [1] and the development of
Memento clients such as the FireFox add-on MementoFox [2]:

1. Being able to intercept HTTP requests in the client at every step is
critically important for us in order to be able to accurately navigate to
prior versions of resources.  Please imagine the following case:
- 12 months ago, a given URI (R1) redirected to a particular image (I1).
- Today, it redirects to a different image (I2).
In order for a Memento client to be able to retrieve the image that was the
end result of the redirect 12 months ago (I1), it must be able to intercept
the first URI requested (R1) and start time traveling from there. Indeed,
if not intercepting the first URI and hence following the redirect chain,
the Memento client would end up at image I2, which was not the active
resource 12 months ago.
As it is important to be able to do this same interception for any HTTP
request, automatically and unpreventably following links in XMLHttpRequest
or any other context is very disruptive.

2. There is another issue regarding automatic following, which is possibly
tangential to the current discussion, but we feel is worth bringing up.
 The Link Header RFC [3] allows target URIs to be associated in the HTTP
headers with the responding resource.  It would be very useful if users
could set preferences to allow following these links, even if the response
is not a 3XX status. In Memento clients, this would allow to e.g. follow a
link to a TimeGate.

Thank you for the consideration,

Herbert Van de Sompel, Michael Nelson, Robert Sanderson

[1] Memento:  http://mementoweb.org/ ; Internet Draft:
https://datatracker.ietf.org/doc/draft-vandesompel-memento/
[2] https://addons.mozilla.org/en-US/firefox/addon/mementofox/
[3]RFC5988: http://tools.ietf.org/html/rfc5988

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

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