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Re: Comments on LDP TR http://www.w3.org/TR/2013/WD-ldp-20130730/ ( LC-2836)

From: Tim Berners-Lee <timbl@w3.org>
Date: Tue, 10 Dec 2013 21:34:18 -0500
Cc: public-ldp-comments@w3.org, Read-Write-Web <public-rww@w3.org>, Tabulator Developers <tabulator@lists.csail.mit.edu>
Message-Id: <3C61F7D1-763E-4A81-A28D-C73BDCB5B614@w3.org>
To: lehors@us.ibm.com

On 2013-11 -15, at 20:19, lehors@us.ibm.com wrote:

> Dear Tim Berners-Lee ,
> The Linked Data Platform (LDP) Working Group has reviewed the comments you
> sent [1] on the Last Call Working Draft [2] of the Linked Data Platform 1.0
> published on 30 Jul 2013. Thank you for having taken the time to review the
> document and to send us comments!
> The Working Group's response to your comment is included below.
> Please review it carefully and let us know by email at
> public-ldp-comments@w3.org if you agree with it or not before 29 November
> 2013. In case of disagreement, you are requested to provide a specific
> solution for or a path to a consensus with the Working Group. If such a
> consensus cannot be achieved, you will be given the opportunity to raise a
> formal objection which will then be reviewed by the Director during the
> transition of this document to the next stage in the W3C Recommendation
> Track.
> Thanks,
> For the Linked Data Platform (LDP) Working Group,
> Eric Prud'hommeaux
> Yves Lafon
> W3C Staff Contacts
> 1. http://www.w3.org/mid/34BE20B3-86E3-434F-B454-B004E9A338F0@w3.org
> 2. http://www.w3.org/TR/ldp/
> =====
> Your comment on :
>> #########################
>>   303 lis a basically very unsatisfactory design because of the
>> round trip.  As this is a new spec, suggest defined 20X code meaning
>> like a 303 but containing the representation of the thing 303d to.  This
>> has been found to a problem in LD. LDP can avoid it now.
>> Benefit: First page back to user in one less round trip.
>> #########################
>>   This design puts the type and next links in the data.  I
>> prefer I think using HTTP headers here as elsewhere.  Page control stuff
>> is very meta, messy to have it in with actual data.
>> Not a problem for containers, but for normal LDPRs IMHO.
> Working Group Resolution (LC-2836):
> Given the time constraints under which the WG is it is deemed unpractical
> to depend on defining a new response code as suggested. However, based on
> input from several HTTP experts the WG decided to return the first page
> with 200 response code on initial GET which prevents the additional
> roundtrip you objected to.
> See http://www.w3.org/2013/meeting/ldp/2013-11-04#resolution_2

Shame about 209, it was needed for other things as well, all the data which currently uses 303.

Like any LD concept whose URI has no hash.
(What is the WG's take on that -- are hashes being used everywhere?)

So the URI which the client sent in the GET is now overloaded
as being used to identify both the collection and the first page of a collection.

I am trying to understand how I should tweak my code to capture what has happened with the 200. 
There is some large imaginary document which contains all the data of which these are pages, and which has no URI itself, and we have an abstract collection whose IRI is punned with the first page.

Supposing I am making a generic client which can make a SPARQL query over the some linked data, and I want it to work for this situation.    What is its algorithm?    

I can make a function which, if looking at links from x and x is punned with a a page which has a next link, then I fetch all next links, aggregate all the date from them as a representation of the collection document, and then query that.  Is that what I need?

I must be able to determine the state of the collection.

Maybe generically when not doing lazy  evaluation, I just follow all 'next' links wherever I find them, knowing that without doing that I just don't have all the data about them.  Then in my quad store, what is the provence of the triples in the successive pages -- the page or the union of them?

If I want to show that y is NOT in the collection x, then I have to be sure I have looked up x.

It seems a shame to have no URI for the union, and to be overloading the URIs for the first page and the collection.

And questions like that.

Have members of the WG written code to do these things?


> Move Paging information out of the RDF content into HTTP headers.
> See http://www.w3.org/2013/meeting/ldp/2013-09-30#resolution_2
> ----
Received on Wednesday, 11 December 2013 02:34:24 UTC

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