Bill de hÓra (on a Danny Ayers post):

In other words, the work of generating RDF will be placed on people who want to use RDF. I think this idea of extracting RDF from published markup instead of using RDF as the backing data to generate the published markup is a big deal. For one, it will mean less RDF tax on existing publishers, who seem to be happy to stay with HTML, RSS and microformats (uF). Second it distributes costs fairly - RDF proponents will be forced to derive value from what they extract instead of playing schedule chicken with publishers, and pushing costs back onto them to supply the data just so. Third, from a systems design viewpoint, extraction is a much cleaner design than trying to kludge RDF support on top of existing RDBMS storage and web frameworks. It's cheaper today to publish uF via web frameworks, databases and templates than retool internally with RDF based technology - uF by being HTML is a relatively low-impact upgrade on the templating tier, not a rip and replace of the data/object tiers. I've been saying for some time that the Semweb is missing a layer, the one that infers the useful information from syntactic markup. Maybe uF and GRDDL are that layer's ingredients.