Resources (RDFa): A Promising Complement to Microformats

There’s a lot of hype around RDF and the semantic Web, but the core concept of the Resource Description Framework (RDF) is simple:

Tim Bray’s “What is RDF?” ( was the first essay I read in my attempts to understand RDF. It’s still very good. However, I think that the triplets idea was still unclear to me after reading the essay. (And I don’t blame Tim Bray for that since the idea is clearly in the essay.) So, you should follow up Bray’s essay with reading something like Aaron Schwartz’s “RDF Primer Primer” ( The two complement each other.

You can express RDF triplets in many ways, including the standard RDF/XML syntax ( Since we have been discussing how microformats embed ­machine-­understandable data in (X)HTML, we’ll now look at RDFa (http://?, described in the following way:

With RDFa, you can easily include extra “structure” in your HTML to indicate a calendar event, contact information, a document license, etc. . . . RDFa is about total publisher control: you choose which attributes to use, which to reuse from other sites, and how to evolve, over time, the meaning of these attributes.

Here is a sample RDFa assertion, in which the resource (a book with ISBN of 9781590598580) has a property (namely, the Dublin Core title) whose value is Pro Web 2.0 Mashups: Remixing Data and Web Services:[320]

         <span xmlns:dc="" about="isbn:9781590598580"
               property="dc:title">Pro Web 2.0 Mashups: Remixing Data and Web Services</span>

I think that microformats and RDFa will both have a place on the Web. Microformats already have some good uptake and are grounded in today’s ­real-­world problems. They are focused on very specific applications. RDFa provides a mechanism for making more general assertions about pieces of data.