Thoughts on RDFa

Over the past couple of months I’ve been thinking a lot about semantic web — specifically how it fits in with the company’s overall future web development strategy. This has lead me to tinkering with RDFa markup, re-engineering current solutions with more forward thinking, semantic approaches. I have been a big proponent of microformats as a lightweight semantic markup tool (and I still think they have merit), but since have been intrigued and impressed with the power of RDFa. As with all new concepts, RDFa isn’t a “silver bullet” right out of the gate. Sitting down and actually coding the stuff into real-world examples has brought to light some potential issues that may be encountered by developers introducing RDFa to their pages.

Ontology Explosion?

Like RDF/XML, RDFa markup depends on identifying and utilizing specific ontologies in your HTML document. One could create a custom ontology specifically for a single use case. This could result in hundreds or even thousands of custom ontologies for the same concept or object. My fear is that that without proper oversight, the overabundance of ontologies will lead to a decrease in the effectiveness of RDFa, and clutter the semantic web with non-reusable ontologies. Since RDFa is recognized by the W3C, my hope is this group can provide some leadership and governance — possibly working to establish more officially recognized ontologies for use (and reuse!) on a wide scale.

Document Size

Maybe I’m just being old fashioned here, but are people still concerned about HTML document size and performance? I know my company is. In most of my examples, I saw an increase in the amount of HTML markup needed to fully code the page, usually between 5-20%, depending on the complexity of the solution. Efforts will need to be made by developers to streamline their code in order to avoid performance issues due to “heavy” HTML.

Object Order

For some ontologies, object order matters — that is, element y is in the domain of x, and should be nested under the parent. If your web page has a specific visual look and feel, will that match the object order needed to be valid RDFa? While flexible front-end development techniques using CSS will handle most of these instances, I foresee a certain amount of give and take between design/ information architecture staff and developers to achieve a balance of human usability while maintaining the data structure of the document.

Overall, I am convinced that RDFa is the right technology to fuel the semantic web, providing human usability and machine readability, even with the issues described above. In most scenarios, the benefits of delivering rich data directly to the front-end outweigh the effort to implement it. As adoption increases, new techniques will be invented that should alleviate most problems. After all, we developers are a smart bunch