- From: Mark Birbeck <mark.birbeck@webbackplane.com>
- Date: Mon, 29 Jun 2009 13:30:12 +0100
- To: Tom Heath <tom.heath@talis.com>
- Cc: martin.hepp@ebusiness-unibw.org, Kingsley Idehen <kidehen@openlinksw.com>, public-lod@w3.org, semantic-web at W3C <semantic-web@w3c.org>
Hi Tom, On Sun, Jun 28, 2009 at 11:46 PM, Tom Heath<tom.heath@talis.com> wrote: > Martin, > > 2009/6/27 Martin Hepp (UniBW) <martin.hepp@ebusiness-unibw.org>: >> So if this "hidden div / span" approach is not feasible, we got a problem. >> >> The reason is that, as beautiful the idea is of using RDFa to make a) the >> human-readable presentation and b) the machine-readable meta-data link to >> the same literals, the problematic is it in reality once the structure of a) >> and b) are very different. >> >> For very simple property-value pairs, embedding RDFa markup is no problem. >> But if you have a bit more complexity at the conceptual level and in >> particular if there are significant differences to the structure of the >> presentation (e.g. in terms of granularity, ordering of elements, etc.), it >> gets very, very messy and hard to maintain. > > Amen. Thank you for writing this. I completely agree. RDFa has some > great use cases but (like any technology) has its limitations. Let's > not oversell it. Mmm...you put me in a difficult position here. :) If I leap to RDFa's defence then it looks like I think it solves all the world's problems. But if I remain silent, then it looks like the problem being raised is some kind of fundamental flaw. Ah well, let's dive in... First I should say that I'd be the first to agree that RDFa has limitations. But the issue here is that I don't think the problem raised by Martin can be classed as a limitation in the way you're implying, Tom. If we go back a step, RDFa was carefully designed so that it could carry any combination of the RDF concepts in an HTML document. In the end we dropped reification and lists, because it didn't seem that the RDF community itself was clear on the future of those, but they are both easily added back if the issues were to be resolved. In short, it is possible to use HTML+RDFa to create complete RDF documents, such as RDF Schemas, OWL ontologies, and so on, and the resulting documents would be no more complex than their equivalent RDF/XML or N3 versions, with the benefit that they can be delivered using any of the many HTML publishing techniques currently available. But most of the discussion around RDFa relates to its other use, where it's possible to use it to 'sprinkle' metadata into HTML documents that are primarily aimed at human readers. By being alongside the human-readable output, it makes the metadata easier to maintain. And in addition it gives the user agent the opportunity to enhance the view of the data, by making use of the 'local' metadata. However, the point that Martin was getting at, is that sometimes there is just way more data in the 'RDF view' than in the 'human view', and that makes it very difficult to make the two align. I don't think that this is a flaw in RDFa itself, and I'm not convinced that there is an easy solution in the form of another technology that would solve this. Martin's solution seems a reasonable one to me. (Although I wonder if part of the problem might be that too much information is being provided in the RDF view, rather than using links to other data that can be retrieved. Perhaps Michael could give an example.) Regards, Mark -- Mark Birbeck, webBackplane mark.birbeck@webBackplane.com 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)
Received on Monday, 29 June 2009 12:30:54 UTC