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Re: Can't RDF describe collection resources?

From: Breslin, John <john.breslin@nuigalway.ie>
Date: Thu, 1 Mar 2012 08:30:40 +0000
Message-ID: <5262D87D-4FFA-4963-B95B-C54AF10254AF@nuigalway.ie>
To: "Ruben Verborgh" <ruben.verborgh@ugent.be>
Cc: "Michael Hausenblas" <michael.hausenblas@deri.org>, <public-rdf@w3.org>, <public-rdf-wg@w3.org>, "W3C SWIG Mailing-List" <semantic-web@w3.org>
Hi Ruben

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...

John
http://bresl.in


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 08:31:21 GMT

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