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Re: RDFa and the owl:Thing class

From: Ivan Herman <ivan@w3.org>
Date: Wed, 11 Feb 2009 13:15:49 +0100
Message-ID: <4992C175.1020705@w3.org>
To: Sandy Pérez <sperezgonza@yahoo.es>
CC: public-rdf-in-xhtml-tf@w3.org
Dear Sandy,

thank you for your interest in RDFa, first of all.

I am afraid there are some misunderstandings, though. 'owl:Thing' is a
particular class in the OWL vocabulary. It is not a necessary part of
any RDF vocabulary. There is of course no problem in using it if you use
the OWL vocabulary but that has to be done explicitly.

In view of this, let me comment on your questions below:

Sandy Pérez wrote:
> Hello,
> I am writing because I have a doubt about RDFa. What happens with
> owl:Thing class? I’m testing RDFa using an ontology for tags
> (http://code.google.com/p/tagont/). In this ontology, the resource to
> be tagged is an owl:Thing, so, how can I annotated resources
> (owl:Thing) using RDFa? I suppose if I create an ontology containing
> the class "Resource", I could annotate it as follows:
> <div    xmlns:myResources=”http://www.mydomain.com/myResource”
>         xmlns:myOntology=” http://www.mydomain.com/resourceOntology”
>         xmlns:tagont="http://bubb.ghb.fh-furtwangen.de/TagOnt/tagont.owl"
>         typeof="myOntology:Resource" about="myResources:ResourceID">
> …
> </div>
> However, I would not like to create a new ontology since the ontology
> for tags contains the concept "Resource" supported as an owl:Thing. Is
> the following example a correct option?
> <div    xmlns:myResources=”http://www.mydomain.com/myResource”
>         xmlns:tagont="http://bubb.ghb.fh-furtwangen.de/TagOnt/tagont.owl"
>         typeof="owl:Thing" about="myResources:ResourceID">
> …
> </div>

Almost true. Three issues. Actually, only the first is related to your
original question, but I took the liberty of pointing out two more small
problems. I hope that is all right. So:

- You have to add a namespace declaration for owl, too, to get the
owl:Thing as a type. Ie, the


if you do that than what you write is correct (modulo the points below)
and does what you want!

- The namespace URI-s you use may not be the right ones. In RDFa, these
are essentially prefixes to be concatenated with whatever is in the
attribute values. I presume what you want to have is


which means that you should add the '#' character to the end of the URI

- There is another small bug in your code. The value of @about is
defined to be either a URI or what is called a 'safe curie'. Ie, to
achieve what you want, it should say @about="[myResources:ResourceID]"
or @about="http://www.mydomain.com/myResource#ResourceID

> If that’s the case, as everything is an owl:Thing, is it possible to
> omitted the "typeof"  attribute? For example:
> <div    xmlns:myResources=”http://www.mydomain.com/myResource”
>         xmlns:tagont="http://bubb.ghb.fh-furtwangen.de/TagOnt/tagont.owl"
>         about="myResources:ResourceID">
> …
> </div>

As I said: it is not true that everything is an owl:Thing. This is for
individuals in the OWL vocabulary, but not for RDF in general.
Consequently, there is no such default in RDFa (or any other RDF

What _is_ true, however, is that everything is an rdfs:Resource! That is
true for RDF in general and, indeed, there is no need to explicitly
declare this type for a particular URI.

> I am sorry if the previous questions are trivial. I am interested in
> RDFa but I am newbie using it.

There are no trivial questions when you start learning these things...
Thanks for your interest!


> Thanks in advance,
> Best Regards,
>     Sandy
>     mailto:sperezgonza@yahoo.es


Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Wednesday, 11 February 2009 12:16:26 UTC

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