RDFa

David Decraene is looking for feedback on his article Embedding OWL-RDFS syntax in XHTML with RDFa, which is a “Short introduction to RDFa, OWL and Microformats”, and aims to come up with:

a solution that reconciles the ease of use of Microformats with the expressivity of a language like OWL. Some problems hindering OWL adoptation will be highlighted, and a first experiment with the use of RDFa mark-up to embed OWL data directly into an XHTML page will be demonstrated, a solution that can be considered as a step higher than Microformats on the evolutionary ladder of the web.

He argues that OWL has a poor presence on the web, attributing this mainly to the fact that no-one has explored approaches to “align / integrate OWL with current web content”:

For ontological data to truly be useful, you need to somehow tie current web content with semantic classes and instances. OWL has failed miserably in this respect so far. It is much like a far away island of Eden, and a man without a canoe. All the important data could be there but no-one knows how to reach it. Granted, OWL does define a standard format for data interchange between applications, but this limited scope cannot be what the semantic vision is about.

Interestingly enough, if you replaced the word ‘OWL’ with the word ‘RDF’, you’d have pretty much the main motivations that spurred the development of RDFa in the first place. David goes on to give an example:

What we need is semantic annotation. You need to be able to tag sections of your content with explicit ontology classes and even relations, without it hindering the display of your content. If you wrote a piece on a certain bordeaux for example, you could mark up the section as being about an instance of wine, perhaps even with some properties defined (or even more amazing, just by knowing it is about wine properties can be extracted automatically, a mention of red is bound to be about the wine color).

Whilst there is no doubt that the kind of complex RDFa David uses in his post is not for the everyday user of RDFa, the fact that RDFa can be used for these kinds of complex examples shows that the architecture is solid.

(This rdfa.info post also appears on XForms and Internet Applications.)

A very interesting application of RDFa has been announced recently: Ontology Online. It is what I would call a Web 3.0 application, using the best of Web 2.0 and Semantic Web - check it out!

Ian Davis has an interesting post about the Shadow Web that may be created if we don’t bridge the existing (”clickable”, as I like to say) web and the semantic web:

Current practice in the Semantic Web community is leading to the creation of a shadow web that is becoming disconnected from the web of documents. This fracturing is being caused by the W3C’s decision to restrict the types of resources that can be addressed directly with HTTP .
[...]
This means that HTML and RDF need to be much more connected than many people expect. In fact I think that the two should never be separate and it’s not enough that you can publish RDF documents, you need to publish visible, browseable and engaging RDF that is meaningful to people. Tabular views are a weak substitute for a rich, readable description.

Ian mentions RDFa as one of the technologies aiming to build this bridge. And Benjamin Nowack responds by pointing out how RDFa plays nicely with the fragment identifier practice of the semantic web.

Over in the public HTML list, a posting by Peter Krantz caught our eye with this line:

I am working in a project right now where RDFa solves a lot of problems for over a 100 government organizations.

Nice to see RDFa gaining traction!

We’ve reached a point where new editors’ drafts of the syntax and processing document, and an introductory primer are available, ready to be reviewed by the W3C’s Semantic Web Deployment Group at their next face-to-face meeting.

Take a look. RDFa is pretty close to completion…and now the fun can really begin.

There’s an interesting discussion going on over at xml-dev about how to mark-up documents that will still need to be around in 20 years time, such as legal documents or financial transactions. A number of ideas have come up, and interestingly one of them is to use RDFa. Now that the RDFa specifications are pretty much complete we’ll soon be able to get involved in these kinds of discussions, and explain how RDFa can provide a solution–indeed it was designed to.

Peter Krantz has some extremely interesting thoughts on the use of RDFa in assistive technologies. It makes thought-provoking reading not just because it raises some interesting ideas about accessibility, but also because it gets us thinking about how we might define a processing model that sits on top of RDFa, that would in turn allow all sorts of functionality. Peter gives an example at the end of his article:

In practice, the sequence of events for a screen reader working on top of a web browser could look like this:

1. Browser opens the web page.
2. Screen reader parses the HTML and extracts references to all external vocabularies.
3. External vocabularies are fetched and parsed for labels and descriptions.
4. The screen reader announce that extended information exists and starts rendering the page.

So, by using RDFa to reduce ambiguity for machines it is likely that humans too can benefit from the added information. It will be very interesting to see what makers of assistive tools can come up with.

Joost — TV over the internet from the makers of Skype — have started using RDFa on their website to classify programs available on their system. For instance, go to http://www.joost.com/0440008, and do a view source, and you will see RDFa attributes being used to describe the program.

For a longer exposition, see Mark Birbeck’s post at http://internet-apps.blogspot.com/2007/07/rdfa-used-in-joost.html.