Posted Apr 29, 2010 19:10 UTC (Thu) by Simetrical (guest, #53439)
Parent article: What is Open Graph?
"In addition to that, WHATWG is working on an alternative semantic markup scheme called Microdata that encodes metadata in HTML attributes rather than in <meta> tags. This technique makes it possible to mark up multiple items in a single page, rather than limiting each page to a single object as in OGP."
Second of all, microdata is not competing with OGP, but with RDFa. Microdata is a way to embed any kind of metadata you like into HTML pages, just like RDFa. Most things you'd want to do with RDFa-in-HTML can also be done with microdata, just with different syntax. E.g., if Facebook had decided to release OGP as microdata instead of RDFa, it would probably be something like
This uses <meta> tags, but both RDFa and microdata support putting their respective attributes on other tags too, and indeed this is encouraged. I'm pretty sure you don't actually have to use <meta> in OGP as things stand -- you could do something like
<title property="og:title">The Rock</title>
and it should work as you expect, as far as I understand it. If not, it should be something like that. (Microdata is again the same, but with itemprop instead of property.) The OGP examples use only meta tags, but if Facebook is actually using a conformant RDFa implementation (which maybe they aren't), you shouldn't have to use those. Similarly, RDFa supports having many different objects on the same page, as far as I know, and if Facebook doesn't support that, microdata won't make any difference.
Microdata supporters think it should be preferred to RDFa because they believe it's much easier for HTML authors to use. Personally I suspect this is true (and am a microdata supporter!). But in any case, microdata and RDFa can both support simple name-value mappings like this just as easily and with very similar syntax, so this particular standards war isn't really relevant here.