Re: reusing vocabularies / mapping withowl:equivalentClass

Hi Thomas,

There is no such thing as an "RDFa format", since RDFa is merely a way
of marking up RDF; in the same way that you can use RDF/XML or N3 to
'carry' your RDF triples, so too you can use RDFa.

So the "implementation-neutral vocabulary" you want would be in RDF.
If you want to use the property 'dc:title', then you go right ahead
and give something a predicate of "http://purl.org/dc/terms/title".
And you can do that in RDF/XML, N3, RDFa, and so on.

However, you _can't_ do that in MIcroformats, since uF doesn't deal
directly with RDF. Of course you can 'map' it to RDF, and that is
where techniques such as GRDDL come in. So for example, you could
create a mapping that says 'if the string of text "dc-title" appears
in the class attribute, map it to a predicate of
"http://purl.org/dc/terms/title"'. But you could just as easily create
a GRDDL transformation that turns "banana" into
"http://purl.org/dc/terms/title" if you wanted to. The key point is
that the uF 'value' does not equate to RDF in any sense other than by
popular conventions.

That's not the same for RDFa, though. As with N3 or RDF/XML, you can
use the URI for a Dublin Core 'title' directly, without any
intervening mapping, because you are using RDF itself.

That's not to say that you shouldn't write a vocabulary that says 'a
recipe title is equivalent to a Dublin Core title', but that would be
going on at the level of your RDF -- hopefully using OWL -- and is not
imposed upon you by RDFa or uF's (the former because it doesn't need
it, and the latter because no matter what you do you have to do a
mapping anyway). But if it was me, I wouldn't bother; returning to
your core question, on whether to reuse or invent, I would just go
ahead and use dc:title directly in my recipe vocabulary, since its
definition is easily broad enough to encompass things like recipes.

But that's to some extent personal taste, and the key point --
regardless of whether you use OWL mappings or not -- is that any
mapping you do is happening at the RDF level, and you are doing it
because it helps your RDF.

I hope that helps...

...but I wouldn't be surprised to learn that it hasn't. :)

Regards,

Mark

On Tue, Oct 14, 2008 at 10:48 AM, Thomas Loertsch
<loertsch.thomas@guj.de> wrote:
>
> Hi there,
>
> I want to derive a RDFa format from a microformat, an experimental version
> of hRecipe in this case. I think of them both as serializations of a
> vocabulary. To make the distiction clearer I'll call them vRecipe (the
> implementation-neutral voacbulary), hRecipe (the microformat) and aRecipe
> (the RDFa format).
>
> I'm unsure how to map the vRecipe to RDFa. Should I reuse existing
> vocabularies or should I develop a new one and then provide an OWL mapping
> to existing vocabularies?
>
> E.g. there's a title-element in vRecipe, called 'recipe-title'. In hRecipe,
> the microformat serialization, it's called 'recipe-title' as well. Since
> RDFa provides namespacing mechanisms it could be called 'hRecipe:title'
> here. A mapping from 'hRecipe:title' to 'DC:title' -
>
>    hRecipe:title owl:equivalentClass dc:title
>
> - would make it clear that both are semantically equivalent. Although in
> this example it's not obvious why not to use a straightforward mapping to
> the wellknown DC:title in the first place, but the whole vRecipe vocabulary
> needs mappings to a whole bunch of other vocabularies, some of them not so
> well known, and it looks quite messy when mapped straightforwardly. It would
> surely look much prettier - and was much easier to comprehend and use - if
> it was developed from scratch (and from the vRecipe voacbulary respectively)
> in a coherent way and *then* mapped to other, already existing vocabularies
> with owl:equivalentClass.
>
> I can see that the use of OWL adds complexity and that OWL can't be handled
> "meaningfully" by simple RDF tools but I'm not sure how much of a problem
> that is. Simple RDF tools can surely parse it which would be enough for a
> lot of usage scenarios. The whole power of the semantic web otoh only comes
> with RDFS and OWL and therefor it seems okay to me to use them like I did
> above. Or am I adding complexity where I really shouldn't?
>
> Cheers,
> Thomas
>
>
> ..
> Thomas Lörtsch
> Living at Home Multi Media GmbH
> Redaktion Online
> ...
> Stubbenhuk 5
> 20459 Hamburg
> ....
> eMail: loertsch.thomas@guj.de
>
>
>
>
>
>



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Mark Birbeck, webBackplane

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http://webBackplane.com/mark-birbeck

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Received on Tuesday, 14 October 2008 13:03:40 UTC