W3C home > Mailing lists > Public > public-webid@w3.org > February 2013

Re: 303 and HTTPbis

From: Mo McRoberts <Mo.McRoberts@bbc.co.uk>
Date: Fri, 22 Feb 2013 15:32:45 +0000
To: Ted Thibodeau Jr <tthibodeau@openlinksw.com>
CC: Henry Story <henry.story@bblfish.net>, WebID Group <public-webid@w3.org>
Message-ID: <C664BBE6-0B31-4F00-AF28-43BBF07D9F56@bbc.co.uk>
Yes, that's essentially codification of Content-Location as a 200 response header, if you think about it.

However, something which is often missed is that there may not be two, but *three* separate URIs that you want to refer to:

1 - The document (in any form)

2 - The document as expressed in a specific serialisation

3 - The thing described by the document

For example (using common patterns):

1 - /things/1234 – used as a Request-URI and results in conneg.

2 - /things/1234.ttl — sent as Content-Location, the specific serialisation of /things/1234 as text/turtle (along with /things/1234.jsonld, /things/1234.html, etc., etc.); sent in an Alternates response header if you're so inclined; can be requested explicitly for debugging if needed.

3 - /things/1234#thing - the thing described by /things/1234, and the URI which is plugged into your agent

The reason for this is that it can be useful to describe both the document and the serialisation independently of each other, because although one is an expression of the other, they can have different values for the same properties of descriptive metadata.

As it goes, I you could express it with 303 and a redirect:

1 - /resources/1234

2 - /resources/1234.ttl (or /resources/1234/turtle, or whatever you wanted to do)

3 - /id/1234

(i.e., a request for (3) results in a 303 redirect to (1) which returns a 200 with a Content-Location of (2))

I can't fathom a clean way of doing that with an initial 200 response.

HOWEVER, I also suspect it's not going to matter in practice for most WebID uses, except for somebody wanting to be consistent with practices used elsewhere, or because the author of the profile document is particularly complete-ist…


On Fri 2013-Feb-22, at 15:03, Ted Thibodeau Jr <tthibodeau@openlinksw.com>

> On Feb 20, 2013, at 10:37 AM, Henry Story wrote:
>> But this makes clear that even for HTTPBis there are still two HTTP Connections required to get from a non hash WebID to a WebID Profile:
>> 1. The first GET on the WebID returns a 303 with a Location header
>> 2. The second GET on the Location retrieves the Profile Document
>> This means that the advantage of 303s with respect to caching of the content of 303s goes only so far as to allow a client to cache a 303 header (which means that the time to live of the redirect for example makes some sense) But the main inefficiency of redirects still remains. Even SPDY could not resolve this problem.
> *Except* that the 303 redirect followed by a second GET is
> *not required*.
> The server *may* return a 200 OK with appropriate HTTP headers
> and such, which indicate that the original GET isn't being
> returned, but the closest matching thing is -- and expressing
> the URI and MIME type of that closest matching thing -- thereby
> saving the second GET by pre-emptively delivering its result.
> If absolutely necessary, I'll invest the time in scouring the
> specs for where this is discussed -- but it's already been done
> several times in several other groups, and I assure you, this
> is there.
> Regards,
> Ted
> --
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Received on Friday, 22 February 2013 15:33:18 UTC

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