At SXSW today Eric Meyer gave a talk on Emergent Semantics. He humorously described emergent as a fancy way of saying grassroots, groundup (from the bottom or like ground beef), or evolutionary. The talk was about adding rel attributes to XHTML <a> elements, or the lowercase semantic web, or Semantic XHTML, of which I am a fan.

Unfortunately Eric made some incorrect statements about the uppercase Semantic Web, or RDF/RDFS/OWL, of which I am also a fan. First, he implied that the lowercase semantic web is to the Semantic Web as evolution is to intelligent design, the current last redoubt of apolgists for theism.

Very much related to this analogy, Eric stressed that use of Semantic XHTML is ad hoc and easy to experiment with, while the Semantic Web requires getting a committee to agree on an ontology.

Not true! Just using rel="foo" is equivalent to using a http://example.com/foo RDF property (though the meaning of the RDF property is better defined — it applies to a URI, while the application of the implicit rel property is loose).

In the case of more complex formats, an individual can define something like hCard (lowercase) or vCard-RDF (uppercase).

No committee approval is required in any of the above examples. vCard-RDF happens to have been submitted to the W3C, but doing so is absolutely not required, as I know from personal experience at Bitzi and Creative Commons, both of which use RDF never approved by committee.

At best there may be a tendency for people using RDF to try to get consensus on vocabulary before deployment while there may be a tendency for people using Semantic XHTML to throw keywords at the wall and see if they stick (however, Eric mentioned that the XFN (lowercase) core group debated whether to include me in the first release of their spec). Neither technology mandates either approach. If either of these tendencies to exist, they must be cultural.

I think there is value in the ad hoc culture and more importantly closeness of Semantic XHTML assertions to human readable markup of the lowercase semantic web and the rigor of the uppercase Semantic Web.

It may be useful to transform a rel="" assertions to RDF assertions via GRDDL or a GRDDL-inspired XMDP transformation.

I will find it useful to bring RDF into XHTML, probably via RDF/A, which I like to call Hard Core Semantic XHTML.

Marc Canter as usual expressed himself from the audience (and on his blog). Among other things Marc asked why Eric didn’t use the word metadata. I don’t recall Eric’s answer, but I commend him for not using the term. I’d be even happier if we could avoid the word semantic as well. Those are rants for another time.

Addendum: I didn’t make it to the session this afternoon, but Tantek Çelik‘s slides for The Elements of Meaningful XHTML are an excellent introduction to Semantic XHTML for anyone familiar with [X]HTML.

Addendum 20050314: Eric Meyer has posted his slides.