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Re: Can't RDF describe collection resources?

From: Ruben Verborgh <ruben.verborgh@ugent.be>
Date: Thu, 1 Mar 2012 09:36:21 +0100
Cc: "Michael Hausenblas" <michael.hausenblas@deri.org>, <public-rdf@w3.org>, <public-rdf-wg@w3.org>, "W3C SWIG Mailing-List" <semantic-web@w3.org>
Message-Id: <600E3EEC-E64B-4861-99DF-327A491433F5@ugent.be>
To: "Breslin, John" <john.breslin@nuigalway.ie>
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 08:37:02 GMT

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