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Re: Proposal to close ISSUE-19: Adressing more error cases, as is

From: Alexandre Bertails <bertails@w3.org>
Date: Tue, 04 Jun 2013 14:21:54 -0400
Message-ID: <51AE3042.9080005@w3.org>
To: Henry Story <henry.story@bblfish.net>
CC: Mark Baker <mark@zepheira.com>, Kingsley Idehen <kidehen@openlinksw.com>, "public-ldp@w3.org" <public-ldp@w3.org>
On 06/04/2013 01:55 PM, Henry Story wrote:
> On 4 Jun 2013, at 19:42, Alexandre Bertails <bertails@w3.org> wrote:
>> On 06/04/2013 01:10 PM, Mark Baker wrote:
>>> On Tue, Jun 4, 2013 at 9:51 AM, Henry Story <henry.story@bblfish.net> wrote:
>>>> The HTTP response code tells the client that this is an error code and not the representation.
>>> This.
>>> Erik, I wish you'd stop invoking the "REST community", when AFAIK,
>>> you, Henry and I are the only ones to have ever given serious,
>>> brain-cramping thought to the relationship of media types to RDF, and
>>> we have you beat 2 to 1 :)
>> RDF was not designed with HTTP interactions in mind.
> I doubt this. The Open World assumption, URIs for names of relations,

URIs, not URLs...

> Tim Berners Lee who organised and orchestrated the development of it,
> who as far as I know is pretty familiar with HTTP,... all this
> goes to tell me that RDF Was designed very much with HTTP in mind.

RDF semantics is pretty clear about that:
The semantics does not assume any particular relationship between the
denotation of a URI reference and a document or Web resource which can
be retrieved by using that URI reference in an HTTP transfer protocol,
or any entity which is considered to be the source of such
documents. Such a requirement could be added as a semantic extension

At most, RDF is HTTP friendly. For example, that's why SPARQL does not
operate on datasets living on the web (the dataset is behind the
service), and you need to interact with the resources through the
service, whether they are HTTP URIs or not.

> That not everybody understood the full picture is another matter.

The problem with the "full picture" is that anybody can fit anything
that is not yet clearly defined in a document. With that reasoning,
you could argue that LDP was always part of the full picture :-)

>> If I see
>> "Content-type: text/turtle", I know that I should look at [1] to know
>> about the interactions it allows, but this one does not say anything
>> about LDP. At best, I know about the ontology but nothing more.
> [1] is not about interactions. [1] tells you how to parse the result and
> how to interpret it. That is what mime types do, they allow you to select
> among the possible grammers, the ones that you need to interpret the stream
> of bytes on the wire.

That's not how it works. We register the media-type at IANA to say
what is a text/turtle resource. For now, it's still pointing to the
Team Submission. Then it will be the REC when the time comes. If you
don't know about LDP, then there is no way for you to know what
interactions you can have with a text/turtle resource.

>> To be honest, I've never been sure how LDP was solving this issue. I'd
>> be happy to know the general answer.
> So by now, I no longer no what issue you are talking about.
> I can guess. If you get a 401 and you have a well known ontology of
> error descriptions, and the error description says something like
> HTTP/1.1 403 Forbidden
> Content-Type: text/turtle
> Content-Language: en
> @prefix : <http://problems.example/#>
> ...
> <> :hasproblem   [ a <http://example.com/probs/out-of-credit>;
>          dc:title "You do not have enough credit.";
>          atom:summary "Your current balance is 30, but that costs 50.";
>          :problemInstance  <http://example.net/account/12345/msgs/abc>;
>          :balance [ currency:dollars 30 ],
>          :accounts  ( <http://example.net/account/12345>,
>                       <http://example.net/account/67890> ) .
> What else do you need? The 403 tells you that your transaction was forbidden, and so the
> content can only be an explanation of the problem, not a description of the resource.

It's about re-using a standard. The Problem Details spec is general
enough to be adapted to our case just by adapting the model to
RDF/Turtle (what you did in your example). You can decide to take part
of it, that's an option of course but that's a missed occasion.


> Henry
>> Alexandre.
>> [1] http://www.w3.org/TR/turtle/
>>> Mark.
> Social Web Architect
> http://bblfish.net/
Received on Tuesday, 4 June 2013 18:21:56 UTC

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