Re: Can't RDF describe collection resources?

On 01/03/2012 08:58, Ruben Verborgh wrote:
[..]

> The document at [2] does convey the intention that comments is the collection of all comment resources and can indeed nicely generate those triples.
> Can it make the relation between the blog post and the comments collection?

I think you might have me there, i.e. I fear the answer might be no. You 
want

<http://ugent.be/posts/35/> :ifItHasAnyCommentsTheyHaveAUriLike 
<http://ugent.be/posts/35/comments>

We didn't cover that one. I think you'd probably have to use a SPARQL 
query to look for comments, perhaps making use of NOT EXISTS

> (Also if there are no comments?)
>

[..]
> For us, this mismatch is a problem, as we are describing resources in hypermedia APIs and the relations between those resources in RDF.
> Unfortunately, in the REST community, making assertions from URI patterns is also not well-received.

Indeed. POWDER is an attempt to square that circle with rigorous 
semantics. Whether that is sufficient, only time will tell.

>
> I’ll look into POWDER now!

If you find it comes close to fulfilling your needs, let me know if I 
can help.

>
> Thanks,
>
> Ruben
>
>> [2] http://philarcher.org/powder/blogcomments.xml
>
>
>
>> On 01/03/2012 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,
>>
>> --
>>
>> Phil Archer
>> http://philarcher.org/
>> +44 (0)7887 767755
>> @philarcher1
>
>

-- 

Phil Archer
http://philarcher.org/
+44 (0)7887 767755
@philarcher1

Received on Thursday, 1 March 2012 09:33:24 UTC