According to HTML5 spec, every attribute that starts with data- should be ignored by browser and considered a data needed for some scripts. For example:

<ul data-sortable="yes">…</ul>

Does it remind you of something? It is a simplified version of XML namespaces, but limited to non-hierarchical data and with much more probability of data clash.

John Resig, in the comments to his blog post on the matter, says that “The learning curve and failure rate are too high to purely XML-based markup, which is why the data-* attribute exists as a means to implementing this solution”. I completely disagree with the learning curve argument, and this is why:

Programming is complex.

It is easy to forget about the complexity while doing smart new stuff. And new cool things is not what I am talking about. Inventing new thing is easy, since you do not have to think about all limitations of the new ones. Making them work for all occasions, that is what is complex.

It is easy to praise HTML5 over XHTML. It is easy to praise microformats.

But all standards are here for a reason. It is easy to punch Microsoft, however first versions of Google’s Picasa didn’t support non-English text in labels, at all. Current version of Adobe Buzzword does not support Russian text. Current versions of Picasa and Opera do not support Drag&Drop outside of application. I have never seen any of such problems in MS applications. In fact, Visual Basic supported Unicode for ages, while relatively modern web languages stumble on it.

I have already blogged about microformats being a hack. And now I read about BBC removing microformats support due to problems with screen readers and semantics of abbr tag. Is it easy to remember that screen readers must be supported? No. Is it a shiny 2.0 kind-of-thing to think about them? No. But it is one of the multiple things you have to think about when making a wide-used standard.

Adding easy solutions when possible is a great thing. But it wrong to think of programmers as people who can only work with easy solutions. Flexibility is much more important than ease of use, and that’s the lesson that produced, for example, ASP.NET MVC. Also, easy ways should exists as shortcuts for flexible ones, not be orthogonal to them.

And while HTML may be about design, and text processing, and other things, data-* is about programming.