(Public notice: anyone sick of document-versus-thing debates and 303
redirects may safely skip this message! ;-)
On 14 Jul 2008, at 17:38, Mark Birbeck wrote:
Let's flip the whole thing on its head, to begin with. Let's say that
our RDF/XML document is referring to a car:
<rdf:Description rdf:about="http://cars.org/123456";>
<dc:creator>BMW</dc:creator>
<dc:date>2008-07-14</dc:date>
...
</rdf:Description>
That's fine, and we could have hundreds of cars in our RDF/XML
document. However, let's stick to one car, and serve it from the same
URL as its subject.
HTTP has an axiom: If you serve something at a URI, then the URI
identifies a document.
All the troubles you describe below are caused by your attempt to
publish the RDF/XML at the car's URI. This triggers the axiom and
turns the thing into a document. So now you have a resource that
evidently is a car and a document. If that causes problems, then DON'T
DO THAT.
As per [1], either use a hash URI like <cars.org/123456#it> for the
car, or configure a 303 redirect from <cars.org/123456> to, say,
<cars.org/123456.rdf> and serve the RDF/XML there.
Note that if you follow this advice and publish the RDF/XML at
<cars.org/123456.rdf>, then it's perfectly fine to add some extra
triples, such as
<cars.org/123456.rdf> dc:publisher "Richard" .
<cars.org/123456.rdf> foaf:primaryTopic <cars.org/123456> .
So: Yes, RDF/XML documents can talk about themselves.
But: Usually, in an RDF/XML document, you want to talk about
*something else* than the document itself, so give a different URI to
that other thing! That's what hash URIs and 303 URIs are for.
Best,
Richard
[1] http://www.w3.org/TR/cooluris/
As you rightly say we can abbreviate the @about to
refer to the 'current document':
At http://cars.org/123456:
<rdf:Description rdf:about="">
<dc:creator>BMW</dc:creator>
<dc:date>2008-07-14</dc:date>
...
</rdf:Description>
Hopefully that is still so far so good. Now let's add your publisher
information:
At http://cars.org/123456:
<rdf:Description rdf:about="">
<dc:creator>BMW</dc:creator>
<dc:publisher>Richard</dc:publisher>
<dc:date>2008-07-14</dc:date>
...
</rdf:Description>
Why does dc:publisher suddenly apply to the document and not the car?
If it does, how did you (or your software) know to apply it that way?
And even if you knew that dc:publisher applies to documents, (a) how
do you know to apply it to the RDF/XML document, and not
<http://cars.org/123456> (which might be a document), and (b) even if
you can resolve that, how would you decide what to apply the dc:date
to? Should it apply to the car or to the RDF/XML document?
For these reasons I have always viewed RDF/XML as 'scaffolding' that
holds triples which can be about *anything* you like...anything, that
is, except itself. :)
Regards,
Mark
--
Mark Birbeck, webBackplane
[EMAIL PROTECTED]
http://webBackplane.com/mark-birbeck
webBackplane is a trading name of Backplane Ltd. (company number
05972288, registered office: 2nd Floor, 69/85 Tabernacle Street,
London, EC2A 4RR)
