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Fwd: Can't RDF describe collection resources?

From: Jun Zhao <jun.zhao@zoo.ox.ac.uk>
Date: Thu, 1 Mar 2012 09:46:26 +0100
Message-Id: <3F0D0BA9-BC52-4308-AFFB-C15187663054@zoo.ox.ac.uk>
To: Provenance Working Group <public-prov-wg@w3.org>
I think this thread is a good example for us NOT to dive too deep into the modelling of collection in prov. every domain requires their own structure and we need to be as flexible as possible to be an 'interchange' language.

-- jun

Begin forwarded message:

> From: Ruben Verborgh <ruben.verborgh@ugent.be>
> Date: 1 March 2012 09:36:21 CET
> To: "Breslin, John" <john.breslin@nuigalway.ie>
> Cc: Michael Hausenblas <michael.hausenblas@deri.org>, "public-rdf@w3.org" <public-rdf@w3.org>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>, W3C SWIG Mailing-List <semantic-web@w3.org>
> Subject: Re: Can't RDF describe collection resources?
> 
> Hi John,
> 
>> You want to point to the set of replies? You could bundle the Posts or sioct:Comments into a Container or Thread.
>> 
>> But I guess what you need is a has_reply_set property or has_replies / has_comments. You lose the thread structure though if they are all in one container…
> 
> That’s indeed what this specific example needs. But I’m more looking for a general solution that solves this problem for all collection cases.
> It would just not be practical to create a plural property and a singular property for *all* properties out there.
> So what would be the generic “has_replies” solution?
> 
> Best,
> 
> Ruben
> 
>> 
>> On 1 Mar 2012, at 08:22, "Ruben Verborgh" <ruben.verborgh@ugent.be> wrote:
>> 
>>> Hi Michael,
>>> 
>>>> Are you aware of http://sioc-project.org/ …?
>>> 
>>> Thanks for your reply. I’m aware of the SIOC project.
>>> As far as I can see, they do not have a solution for this problem. While they have the :has_reply predicate, they do not have a mechanism to identify all replies to a post.
>>> 
>>> Note that the “blog post” use case is just an example. In fact, it could be anything collection-related (the relation from a book to its reviews, from a social graph to its members, …).
>>> 
>>> The general question is:
>>> RDF is great to express individual relations between resources A and B1, B2, B3…
>>> but how can it express the relation between A and the set of all resources Bx?
>>> 
>>> Best,
>>> 
>>> Ruben
>>> 
>>>> On 1 Mar 2012, at 07:28, Ruben Verborgh wrote:
>>>> 
>>>>> Dear Semantic Web enthousiasts,
>>>>> 
>>>>> Suppose we have a Web application for blogging:
>>>>> - /posts/35 is a blog post
>>>>> - /posts/35/comments are the comments to that post
>>>>> - /posts/35/comments/3 is a specific comment to this post
>>>>> 
>>>>> In RDF, it is straightforward to make the relation between the blog post and a specific comment:
>>>>> </posts/35> :hasComment </posts/35/comments/3>.
>>>>> It is also easy to describe the relation between a specific comment and all comments:
>>>>> </posts/35/comments/4> :memberOf </posts/35/comments>.
>>>>> 
>>>>> However, how do we indicate the relationship between the blog post and *all* comments that belong to it?
>>>>> I.e., what is the relationship between </posts/35> and </posts/35/comments> ?
>>>>> 
>>>>> One could make a new predicate for that of course:
>>>>> </posts/35/> :hasComments </posts/35/comments>.
>>>>> But then, we still have to explain the relation between :hasComments and :hasComment; and we’d have to do that for every such plural predicate.
>>>>> 
>>>>> This seems to be a fundamental problem.
>>>>> Clearly, the resource “comments on blog post 35” exists, but there doesn’t seem to be a straightforward way to describe it in RDF.
>>>>> RDF lists will not be sufficient: they could indeed explain the relation between a specific comment and all comments, but not the relation between all comments and the blog post.
>>>>> Also note that the indirect relation “_:x :hasComment _:y. _:y :memberOf _:z” is not sufficient: a blog post can have no comments, but even then it still has an (empty) comments resource.
>>>>> 
>>>>> Have you encountered this issue and how do you solve it?
>>>>> 
>>>>> Kind regards,
>>>>> -- 
>>>>> Ruben Verborgh
>>>>> http://twitter.com/RubenVerborgh
>>>>> PhD Student at Multimedia Lab – IBBT / ELIS, Ghent University, Belgium
>>>>> 
>>>>> Make your hypermedia API ready for intelligent agents via http://restdesc.org/.
>>>>> 
>>>>> 
>>>> 
>>> 
>>> 
> 
> 
Received on Thursday, 1 March 2012 08:46:58 GMT

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