W3C home > Mailing lists > Public > semantic-web@w3.org > February 2012

Re: [http-range14] how to publish RDF for Information Resources

From: Yang Squared <yang.square@gmail.com>
Date: Fri, 17 Feb 2012 19:26:25 +0000
Message-ID: <CABi4B8D6YkBuR+Z_BAvQ4EXOr-f0iLiisk3fF1OT+orABnS=_w@mail.gmail.com>
To: Leo Sauermann <leo.sauermann@gnowsis.com>
Cc: "Andrea Splendiani (RRes-Roth)" <andrea.splendiani@rothamsted.ac.uk>, "<sergio.fernandez@fundacionctic.org>" <sergio.fernandez@fundacionctic.org>, "<david@dbooth.org>" <david@dbooth.org>, "<semantic-web@w3.org>" <semantic-web@w3.org>
Hi Leo,

Thanks for the link. I think this document mainly focus on discussing the
how to publish URI for non-information resources. URI idnetifies the thing,
real world object.

My question was about how to publish RDF describes
the Information resources, like a webpage.

Thanks,
Yang



On Fri, Feb 17, 2012 at 6:37 PM, Leo Sauermann <leo.sauermann@gnowsis.com>wrote:

>  Hey fellas,
>
> Did you check out the W3C interest group note we wrote on how to make
> these uris and how to do the 303 or #-uris?
>
> http://www.w3.org/TR/cooluris/
>
> this was the original question:
>
> "when I dereferencing the original http://example.com/homepage.html it
> did not result as a homepage.html itself and got a RDF. So there is a
> paradox here."
>
> This question has been answered in cooluris in length.
> (the document explains what timbl and the TAG meant with http-range14 and
> extends it with best-practices found)
>
> also check out:
> http://linkeddatabook.com/editions/1.0/
>
> (p.s.: this http-range-14 (or "uricrisis") question pops up every week
> here since 2001, and usually people do not point the asking person to the
> W3C note nor Bizer's excellent guides that exist since ~2007. it took us
> months to write the guides. I wonder why they are not so popular.
> Really - why? :-)
>
> The discussion of scenario 1 and 2 have been broadly addressed in "cool
> uris", I copy the important bits for your reference:
>
> ...
> ...
>
> The second solution is to use a special HTTP status code, 303 See Other,
> to give an indication that the requested resource is not a regular Web
> document. Web architecture tells you that for a thing resource (URI) it is
> inappropriate to return a 200 because there is, in fact, no suitable
> representation for those resources. However, it is useful to provide
> information about those resources. The W3C's Technical Architecture Group
> proposes in its httpRange-14 resolution<http://lists.w3.org/Archives/Public/www-tag/2005Jun/0039.html>
>  [httpRange <http://www.w3.org/TR/cooluris/#ref-httpRange>] document a
> solution that is to direct you to a document which has information *about*
>  the thing you asked about. By doing this we avoid ambiguity between the
> original, real-world object and the resource that represents it.
>
> Since 303 is a redirect status code, the server can give the location of a
> document that represents the resource. If, on the other hand, a request is
> answered with one of the usual status codes in the 2XX range, like 200 OK,
> then the client knows that the URI identifies a Web document.
>
> If Example Inc. adopts this solution, they could use these URIs to
> represent the company, Alice and Bob:
>  http://www.example.com/id/exampleinc Example Inc., the company
> http://www.example.com/id/bob Bob, the person
> http://www.example.com/id/alice Alice, the person
>
> The Web server would be configured to answer requests to all these URIs
> with a 303 status code and a Location HTTP header that provides the URL
> of a document that represents the resource.* *For example, to redirect
> from http://www.example.com/id/alice to http://www.example.com/doc/alice.
>
> Content-negotiation is then used when retrieving a representation from the
> document URI using a HTTP request. The server decides (see Section 4.7<http://www.w3.org/TR/cooluris/#implementation>)
> to return either HTML or RDF (or more alternative forms) and sets the
> Content-Location header to the URI where the specific representation can
> be retrieved.
>
> This setup should be used when the RDF and HTML (and possibly more
> alternative representations) convey the *same information in different
> forms*. When the information in the variations differs considerably, the
> 303 approach as described below <http://www.w3.org/TR/cooluris/#r303uri> should
> be used.
>
> See the following illustration for the solution providing the generic
> document URI.
>
> [image: solution for a generic document URI]
>
> In this setup, the server forwards from the identification URI to the
> generic document URI. This has the advantage that clients can bookmark and
> further work with the generic document. A user having a RDF-capable client
> could bookmark the document, and mail it to another user (or device) which
> then dereferences it and gets the HTML *or* the RDF view. Also, the
> server can add representations in new languages in the future. Just because
> the client started with the URI of a thing, it doesn't mean that the
> document involved is not a first class document on the WWW. The background
> of generic document resources is described in [GenRes<http://www.w3.org/TR/cooluris/#ref-GenRes>
> ].
> 4.3. 303 URIs forwarding to Different Documents
>
> When the RDF and HTML representations of the resource differ
> substantially, the previous setup should not be used. They are not two
> versions of the same document, but different documents altogether. Again,
> the Web server would be configured to answer requests with a 303 status
> code and a Location HTTP header that provides the URL of a document that
> represents the resource.
>
> The following picture shows the redirects for the 303 URI solution without
> the generic document URI:
>
> [image: The 303 URI solution]
>
> The server could employ content negotiation (see Section 2.1.<http://www.w3.org/TR/cooluris/#conneg>)
> to send either the URL of an HTML description or RDF. HTTP requests for
> HTML content would be redirected to the HTML URLs we gave in Section 2<http://www.w3.org/TR/cooluris/#oldweb>.
> Requests for RDF data would be redirected to RDF documents, such as:
>  http://www.example.com/data/exampleinc RDF document describing Example
> Inc., the company http://www.example.com/data/bob RDF document describing
> Bob, the person http://www.example.com/data/alice RDF document describing
> Alice, the person
>
> Each of the RDF documents would contain statements about the appropriate
> resource, using the original URI, e.g. http://www.example.com/id/alice,
> to identify the described resource.
>
>
> It was Andrea Splendiani (RRes-Roth) who said at the right time 17.02.2012
> 19:21 the following words:
>
> Hi,
>
>  scenario (1): ok. In may also happen to have a third identifier at time,
> for the resource "per se", independently of its representation.
> Note that the *.rdf and *.html resources are distinct information
> resources which refer to the same information content.
>
>  scenario (2):
> You have some data, and some metadata (let's say: creator of an html
> page). If for some specific reason, you need metadata in rdf (and not
> RDFa), then probably a link is the best solution.
> But just to avoid confusion: this is not the general case. In general
> nothing prevents to put you metadata in the html itself (indeed... "meta"
> tags remind of some old intensions). In fact, you may often find a
> copyright statement in the page which is essentially metadata.
> So, if what you propose comes from the fact that you RDF is for metadata
> only, I think that is one possible use of it, not the general case.
>
>  Another thing ti note: nothing says that the document
> http://example.com/data/rdf should contain statements about
> http://example.com/data/rdf. It could very well contain statements about
> the html: http://example.com/homepage.html .
>
>  In conclusion: if you need this separation of metadata in RDF, I would
> go for a link (or RDFa-ish).
> Otherwise in general I would add metadata in both the html and the rdf
> representation. If you are talking specifically about an html file, I would
> add metadata about it (html)in the rdf file. This may be a bit questionable
> at first, but at second I think it makes sense. You don't want infinite
> assertion of meta-* statements ;)
>
>  ciao,
> Andrea
>
>
>   Il giorno 17/feb/2012, alle ore 17.59, Yang Squared ha scritto:
>
> I see your point now. Thx, Andrea.
>
>  I just realise that there may be two scenarios:
>
>  1) RDF and HTML are just the representation of the same resource
>
>  Assume we have a weather report http://example.com/weatherreport which
> has two representation in HTML (human readable representation) and RDF
> (machine readable representation)
>
>  In this case, the content of HTML and RDF should be consistent.
>
>  We can use then using content negotiation to serve these two
> representations for the same URI.
>
>  2) RDF describes a HTML Web Page Resource
>
>  For example
>
>  I have a resource about my homepage http://example.com/homepage.html
> I have a metadata RDF about someone created this homepage
> http://example.com/data/rdf
>
>  In this case, these two URIs are not referring to the same thing.
>
>  According to David Booth and Leo Sauermann, we should use <link> tag in
> HTMl or not widely known HTTP link header (not accepted proposal).
>
>  I hope these are all cases. Please correct me if I am wrong.
>
>  Yang
>
>
>
>
>
> On Fri, Feb 17, 2012 at 5:18 PM, Andrea Splendiani (RRes-Roth) <
> andrea.splendiani@rothamsted.ac.uk> wrote:
>
>> Wait...
>>
>>  http://www.test.com/test.html <- this is a resource, and has it's own
>> URI (1)
>>  http://www.test.com/test.rdf <- this is another resource, and has it's
>> own (distinct) URI (2)
>>
>>  Now, what I am saying is that in the RDF you can also predicate on the
>> the URI (1).
>> So if you ask information about (1), requiring a result in rdf, it seems
>> reasonable to return (2) with predicates (eventually) on (1).
>> This is not really incorrect, though it may be unpractical for some.
>>
>>  But perhaps I don't get your distinction between page and metadata.
>>
>>  Metadata on the page can also be in the html representation itself.
>> In RDF I'm asking for a machine readable representation of the content of
>> the page, rather than it's metadata only.
>>
>>  Do you mean something else by metadata ?
>>
>>  ciao,
>> Andrea
>>
>>
>>
>>  Il giorno 17/feb/2012, alle ore 17.03, Yang Squared ha scritto:
>>
>> Hi Andrea,
>>
>>  I think using content negotiation is incorrect, the homepage is a
>> resource need a URI, and the metadata RDF is another resource need another
>> URI. Otherwise, we are saying the homepage and the metadata of the homepage
>> is the same thing.
>>
>>  The representation of the homepage is the HTML page
>> the representation of the metadata of the homepage is the RDF
>>
>>  Regards,
>> Yang
>>
>>
>> On Fri, Feb 17, 2012 at 4:24 PM, Andrea Splendiani (RRes-Roth) <
>> andrea.splendiani@rothamsted.ac.uk> wrote:
>>
>>> Hi,
>>>
>>>  I'm using content negotiation.
>>> In most of the cases, the "information resource" is actually something
>>> in a database or stored somewhere. So representing it in html or rdf via
>>> content negotiation seems plausible.
>>>
>>>  In case the information resource in html is what you want to predicate
>>> (like, you have a collection of html files that you are serving) the rdf
>>> returned via content negotiation could include predicates about the html
>>> file uri.
>>> If you are asking for the html file resource, this is always in html by
>>> definition. Requesting an rdf implies anyway requesting something else.
>>>
>>>  ciao,
>>> Andrea
>>>
>>>
>>>  Il giorno 17/feb/2012, alle ore 02.21, Yang Squared ha scritto:
>>>
>>>  Hi all,
>>>
>>>  I have a Web architecture question here.
>>>
>>>  Assume I have a information resource URI
>>> http://example.com/homepage.html
>>>
>>>  I would like to publish a RDF metadata (
>>> http://example.com/data/homepagerdf) about this information resource
>>> (e.g. homepage isCreatedBy steve). What publishing mechanism can I use?
>>>
>>>  since http://example.com/homepage.html is an Information Resource,
>>> when dereferencing it, we should get that homepage.html document returned.
>>> How can we possible redirect to a RDF?
>>>
>>>  Content negotiation can use to serve two different representation of
>>> the resource, but both representation is for the same resource. So we
>>> cannot use it.
>>>
>>> 303 can redirect one information resources to another information
>>> resource, e.g. http://example.com/homepage.html --303-->
>>> http://example.com/data/homepagerdf --200-->RDF
>>>
>>>  but in this way, when I dereferencing the original
>>> http://example.com/homepage.html it did not result as a homepage.html
>>> itself and got a RDF. So there is a paradox here.
>>>
>>>  Can anyone please suggest anything? Or the conclusion is that the RDFa
>>> (or by using the link element to RDF) is the only way to publish RDF
>>> metadata for information resources?
>>>
>>>  I am writing a paper and I would like to conclude that there will be
>>> no case that a hashURI publishing mechanism and 303 redirection can be used
>>> for Information Resource to publish RDF metadata. Do you have any object
>>> case?
>>>
>>>  ------------------------------
>>> One may recommend me to use RDFa. However, I consider that the RDFa is
>>> not ideal solution to publish Linked Data at all.
>>> First of all, embedding metadata together with data prohibits the
>>> independent curation of data and metadata. Secondly, following the
>>> principles of the Web Architecture, any distinct resource of significance
>>> should be given a distinct URI, but in this approach a single URI is used
>>> to identify two information resources. In general, the RDFa embedded
>>> metadata approach can be replaced by using the <link> element href in XHTML
>>> to pointing to an external RDF document, where the rel=”meta” attribute
>>> can be used to indicate a relationship between resources.
>>>
>>>  Thanks a lot,
>>> Yang Yang
>>>
>>> -----------------------------------
>>>
>>> Web and Internet Science
>>>
>>> Room 3027 EEE Building
>>>
>>> Electronics and Computer Science
>>>
>>> University of Southampton, SO17 1BJ
>>>
>>>
>>>  Tel: +44(0)23 8059 8346 <%2B44%280%2923%208059%208346>
>>>
>>> twitter: @yang_squared <http://twitter.com/#%21/yang_squared>
>>>
>>>
>>>
>>>
>>>  --
>>>
>>> -----------------------------------
>>>
>>> Web and Internet Science
>>>
>>> Room 3027 EEE Building
>>>
>>> Electronics and Computer Science
>>>
>>> University of Southampton, SO17 1BJ
>>>
>>>
>>>  Tel: +44(0)23 8059 8346
>>>
>>> twitter: @yang_squared <http://twitter.com/#%21/yang_squared>
>>>
>>>
>>>
>>
>>
>>  --
>>
>> -----------------------------------
>>
>> Web and Internet Science
>>
>> Room 3027 EEE Building
>>
>> Electronics and Computer Science
>>
>> University of Southampton, SO17 1BJ
>>
>>
>>  Tel: +44(0)23 8059 8346
>>
>> twitter: @yang_squared <http://twitter.com/#%21/yang_squared>
>>
>>
>>
>
>
>  --
>
> -----------------------------------
>
> Web and Internet Science
>
> Room 3027 EEE Building
>
> Electronics and Computer Science
>
> University of Southampton, SO17 1BJ
>
>
>  Tel: +44(0)23 8059 8346
>
> twitter: @yang_squared <http://twitter.com/#%21/yang_squared>
>
>
>
> --
> Leo Sauermann, Dr.
> CEO and Founder
>
> mail: leo.sauermann@gnowsis.com
> mobile: +43 6991 gnowsis
>
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> ____________________________________________________
>
>


-- 

-----------------------------------

Web and Internet Science

Room 3027 EEE Building

Electronics and Computer Science

University of Southampton, SO17 1BJ


Tel: +44(0)23 8059 8346

twitter: @yang_squared <http://twitter.com/#!/yang_squared>

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Received on Friday, 17 February 2012 19:27:00 UTC

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