eRDF 1.1 Proposal Discussion
The W3C RDFa specification is now in Candidate Recommendation phase, with an explicit call for implementations (of which there are several). Momentum for RDFa is steadily building. What about eRDF, which favors the existing HTML syntax over new attributes?
There’s still a place for a simpler syntactic approach to embedding RDF in HTML, as evidenced by projects like Yahoo! SearchMonkey. And eRDF is still the only game in town when it comes to annotating RDF within HTML-without-the-X.
One thing the RDFa folks did was define src as a subject-bearing node, rather than an object. At first I didn’t like this inversion, but the more I worked with it, the more it made sense. When you have an image, which can’t have children in (X)HTML, it’s very often useful to use the src URL as the subject, with a predicate of perhaps cc:license.
So I propose one single change to eRDF 1.1. Well, actually several changes, since one thing leads to another. The first is to specify that you are using a different version of eRDF. A new profile string of:
The next is changing the meaning of a src value to be a subject, not an object. Perhaps swapping the subject and object. Many existing uses of eRDF involving src already involve properties with readily available inverses. For example:
<!-- eRDF 1.0 --> <img class="foaf.depiction" src="http://example.org/picture" /> <!-- eRDF 1.1 --> <img src="http://example.org/picture" class="foaf.depicts" />
With the inherent limitations of existing syntax, the use case of having a full image URL and a license URL won’t happen. But XHTML2 as well as a HTML5 proposal suggest that adding href to many attributes might come to pass. In which case this possibility opens:
<img src="http://example.org/picture" class="cc.license" href="http://creativecommons.org/licenses/by/2.0/" />