WWW2006 is barely over, and folks are writing about RDFa. This is great news. The enthusiasm and inevitable questions and concerns are very encouraging, and we hope to address these as quickly as we can.
Check out Benjamin Nowack’s careful comparison of RDFa to other metadata embedding techniques. The one downside he points out: RDFa does not currently validate in XHTML 1.0. That’s true, but we had no other choice to achieve the features we need:
- independence: you pick your vocabulary of metadata terms
- modularity: you can reuse other vocabularies
- evolvability: you can change the meaning of your vocabulary over time (yeah, RDF!)
- DRY: don’t repeat yourself, if you render the data in HTML, why repeat it in the structured form?
- in-context: the metadata is right next to the data it describes, and if you copy and paste the HTML, you get the metadata along with it.
But fear not: RDFa does not break anything in today’s browsers. Not even in XHTML strict rendering mode. That’s a big deal, and it means that our upcoming effort to standardize RDFa for XHTML1 is going to be fairly straight-forward.
One significant advantage of RDFa: you can express metadata about other documents (embedded images) and about fragments of the document (a blockquote). And another significant advantage: you can aggregate content from multiple sources, and the metadata schemas will not conflict, thanks to XML namespaces.
Meanwhile, Evan Prodromou compares RDFa to Microformats. He seems worried that the disagreements will be problematic. We don’t think so. Microformats are useful for expressing a few, common, well-defined vocabularies. RDFa is useful for letting publishers mix and match any vocabularies they choose. Both are useful.
And since RDFa is more generic than Microformats, we have a proposal for transforming Microformats to RDFa. We’re still debating this, but it’s very promising. In fact, our calendar bookmarklet uses this technique to read both iCal RDFa, and the hCal microformat.
Ben: how do you see microformats.org and RDFa interrelating a year from now? Two years? Five years? Considering that microformats.org is semantic HTML effort with the most traction right now, don’t you think that it’s worthwhile taking it into consideration?
Is there any value to Web developers and Web users in having both RDFa and microformats?
29 May 2006 at 11:03 pm
[...] Ben Adida notes that people are writing about RDFa, which is great, and envisioning conflict with microformats, which is not. As Ben says: Microformats are useful for expressing a few, common, well-defined vocabularies. RDFa is useful for letting publishers mix and match any vocabularies they choose. Both are useful. [...]
30 May 2006 at 5:03 am
Evan,
Thanks for your comments and blog posting about RDFa. Absolutely microformats need to be taken into consideration. My vision is that, a year or two from now, folks who want to express “just calendar events”, or “just business cards” will be using microformats. People who want to mix and match properties, make up their own, or express metadata about embedded images, page fragments, and the like, will be using RDFa.
My true hope is that, since RDFa is a superset of what can be expressed with Microformats (semantically, not syntactically), we’ll all be using the same tools to parse them. That’s what we’re aiming for with the hGRDDL proposal. You should really take a look at it, because it shows that we’ve been thinking quite hard about how to include microformats, and still address the numerous other use cases that microformats don’t cover.
The most important thing, if you’re using microformats, is to add that profile URL in the head of your document. Without it, building parsing tools for microformats is going to be come very difficult.
31 May 2006 at 7:04 pm