- From: Mark Birbeck <mark.birbeck@x-port.net>
- Date: Thu, 6 Mar 2008 20:46:20 +0000
- To: "Ivan Herman" <ivan@w3.org>
- Cc: "Golda Velez" <gv@btucson.com>, semantic-web@w3.org, ben@adida.net, michael.hausenblas@joanneum.at
HI Ivan, Just a small point on this: > There are some features that RDFa has not defined, ie, not defined to be > automatically generated, and reification is one of those. Simply put, > there was no real demand for it... We did used to have reification (and that probably explains why Golda later in this thread says 'I'm sure someone told me that reification was possible in RDFa'). It was marked up like this: <link rel="p" href="o"> <link rel="whosaidit" href="#me" /> </link> <meta property="p" content="o"> <link rel="whosaidit" href="#me" /> </meta> In short, link and meta placed as children of link and meta, created reified statements. (It's only when applied to link and meta though; a link or meta as a child of statements on a span or div worked in just the same way that a span or div would.) But it turned out that all current browsers do odd things with link and meta when placed in the body of the document, so we were not able to support this syntax for reification in XHTML+RDFa (at least not if we wanted it to work in current browsers). And since the RDF community as a whole doesn't seem to be entirely convinced that reification is the right way to go, we decided that there wasn't exactly pressure to try to find an alternative reification syntax, and so the whole thing was eventually dropped. Speaking for myself, I'm not that bothered. :) I have never liked reification, and I'm a big fan of the named graph approach. The problem with RDF/XML is that you could never 'name the graph' because an RDF/XML document is nothing but metadata...in part why we have the whole 'information resource' v. 'resource' question. But RDFa is slightly different. An XHTML+RDFa document is both a document (an information resource)_and_ some metadata (some resources), and for that reason you could regard the URL of the document as the name of the graph. And using the nice separation that HTML has of head and body, we could put statements about the graph/document in the head (who created it, when, and so on), and the statements themselves in the body: <html> <head about=""> <title>...</title> <meta ...stuff about the graph, like who created it .../> </head> <body about="#"> <span ...stuff about a person, like where they work .../> </body> </html> You could even add an rdf:type for named graph, which I think Jeremy proposed elsewhere: <html> <head about="" instanceof="rdf:Graph???"> <title>...</title> <meta ...stuff about the graph, like who created it .../> </head> <body about="#"> <span ...stuff about a person, like where they work .../> </body> </html> or just imply this automatically when generating triples. Anyway, I don't claim to have worked out all of the ins and outs of this...but it certainly seems quite compelling, and it I think it neatly resolves the information resource questions that often get raised. Regards, Mark -- Mark Birbeck mark.birbeck@x-port.net | +44 (0) 20 7689 9232 http://www.x-port.net | http://internet-apps.blogspot.com x-port.net Ltd. is registered in England and Wales, number 03730711 The registered office is at: 2nd Floor Titchfield House 69-85 Tabernacle Street London EC2A 4RR
Received on Thursday, 6 March 2008 20:46:35 UTC