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Re: Can't RDF describe collection resources?

From: Ruben Verborgh <ruben.verborgh@ugent.be>
Date: Thu, 1 Mar 2012 10:25:03 +0100
Cc: public-rdf@w3.org, public-rdf-wg@w3.org, W3C SWIG Mailing-List <semantic-web@w3.org>
Message-Id: <73A7C44E-39E7-47F0-AFED-07E37503F81C@ugent.be>
To: Enrico Franconi <franconi@inf.unibz.it>
>>> Note that the :hasComment property is redundant in the sense of RDB: its content is equal exactly to the composition of :hasComments and :memberOf. As a matter of fact, the precise and correct way is to use owl property chains as metadata relating :hasComments and :hasComment via :memberOf.
>> Thatís trueóbut it fails if there are no comments to the blog post. Then the comments resource exists (itís just an empty list), but you cannot refer to it because the chaining wonít work.
> No. Think to it relationally: you have a table ":hasComments" which would relate a post to its comments, and a table ":memberOf" relating each set of comments to each specific comment in it. I can have a tuple from a post to its comments, but I do not necessarily have any tuple from such comments to elements. In this case, the derived composed table :hasComment would not have a tuple for that blog post.

Oh, of course, I see it now.
The issue is that RDF in practice always works the other way round: it tends to describe individuals instead of collections.
Plus, I would indeed need to make the relation between plural and singular explicit for each property with OWL property chains. (But at least, itís possible.)


Received on Thursday, 1 March 2012 09:25:40 UTC

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